How to Write Aliens

Aliens — extraterrestrial beings — are central to much science fiction, and writing them well is a specific challenge: making them feel genuinely alien (truly other) rather than "humans in rubber suits," while keeping them comprehensible. Believable aliens have coherent biology (a nature that makes sense), distinct psychology (shaped by that nature), and genuine otherness (real difference from humans), balanced with enough relatability for readers to engage. As a specific kind of nonhuman character, aliens reward thoughtful design. Understanding how to build believable, genuinely-other aliens helps you create the memorable extraterrestrials great sci-fi demands.

This guide covers how to write aliens.

Make aliens genuinely alien

The central goal is making aliens genuinely alien — truly other, not just humans with strange appearances. The classic failure is the "humans in rubber suits" alien — an extraterrestrial that looks different but thinks, behaves, and is essentially human, wasting the point of aliens (their otherness). A genuinely alien being is different at a deep level — in psychology, perception, values, biology, and nature, not just appearance. This deep otherness — aliens that are authentically different in how they think and exist — is what makes them fascinating and true to the concept. So push past the human-in-costume default: design aliens with genuine, deep otherness (in nature and psychology), making them truly extraterrestrial rather than humans in disguise. As with nonhuman characters generally, the otherness must be real and deep, not cosmetic. Making aliens genuinely alien — deeply other — is the defining task. Avoid the rubber-suit trap; build real otherness.

Build coherent alien biology

A foundation for believable aliens is coherent biology — a nature (physical form, biology, environment, evolution) that makes sense and from which the rest flows. Consider your aliens' biology and origins: their physical nature, their environment and how they evolved to suit it, their senses, lifecycle, reproduction, needs, and abilities. This biological coherence (a nature that hangs together logically) grounds the aliens in believability and generates their distinctiveness — their different biology producing different senses, drives, and ways of being. Even modest thought about how an alien's biology and environment would shape them produces more believable, distinctive aliens than arbitrary weirdness. (Real or speculative biology — how different environments and evolution produce different life — can inspire genuinely alien design.) So build coherent alien biology — a logical nature and origin — from which your aliens' distinctiveness flows. Coherent biology grounds believable aliens and generates their genuine otherness. Root your aliens in a sensible, distinctive biology.

Derive psychology from their nature

The deepest otherness comes from aliens' psychology — and the most believable alien psychology is derived from their nature (biology, environment, society). How would beings with this biology, these senses, this environment and evolution, this kind of society think, perceive, value, and behave? An alien's different nature should produce a genuinely different psychology — different drives, ways of thinking, values, sense of self, and worldview, flowing logically from what they are. A hive species, a being with radically different senses, a species with a different lifecycle or relationship to death — each would have a psychology shaped by their nature. Deriving alien psychology from alien nature produces coherent, genuinely-other aliens (their otherness logical, not arbitrary). So derive your aliens' psychology from their nature — letting their biology, environment, and society shape genuinely different minds. Psychology derived from nature gives aliens deep, coherent otherness. This is the heart of believable alien design. Build their minds from their nature.

Keep a thread of relatability

As with all nonhuman characters, aliens need a thread of relatability — enough connection for readers to engage, even amid genuine otherness. An alien so utterly incomprehensible that readers can't relate to anything fails to engage (unless incomprehensibility is the point — some sci-fi explores truly unknowable aliens, a valid but difficult choice). For aliens meant as characters readers connect with, find a bridge: a relatable emotion or drive, a comprehensible goal or struggle, a point of connection across the otherness. This lets readers engage with the alien despite (and often through) its difference. So balance genuine otherness with a thread of relatability: aliens deeply other in nature and psychology, yet with a bridge readers can grasp. (The tension between alien otherness and human relatability is itself a rich source of theme and drama — the challenge of connecting across difference.) Keep a thread of relatability so your genuinely-alien aliens still engage readers. Otherness plus a relatable bridge is the balance.

Use aliens for theme and wonder

Beyond character, aliens are powerful tools for theme and wonder in science fiction. Aliens let you: explore otherness and difference (the encounter with the truly other, and what it reveals about us and connection), reflect on humanity (aliens as a mirror or contrast illuminating the human), create wonder (the awe of genuinely other life and the cosmos), and dramatize themes (communication, prejudice, the unknown, what it means to be a person). The best alien fiction uses aliens meaningfully — not just as monsters or props, but to explore otherness, humanity, and the profound questions of encountering other minds. So consider what your aliens mean and evoke — using them for thematic depth and wonder, not just spectacle. Aliens used for theme and wonder (exploring otherness and illuminating humanity) give sci-fi profound resonance. So design your aliens to evoke wonder and carry meaning, not merely populate the story. Aliens as meaning and wonder elevate the fiction.

The bottom line

Write aliens by making them genuinely alien — truly other in psychology, nature, and perception, not "humans in rubber suits" with strange appearances. Build coherent alien biology — a logical nature, environment, and origin from which their distinctiveness flows — grounding them in believability. Derive their psychology from their nature — letting their biology, environment, and society shape genuinely different minds, drives, and worldviews (the heart of deep, coherent otherness). Keep a thread of relatability — enough connection for readers to engage across the otherness (unless true incomprehensibility is the point), balancing genuine difference with a comprehensible bridge. And use aliens for theme and wonder — exploring otherness, illuminating humanity, and evoking awe, not just spectacle. As a specific nonhuman character, aliens reward this thoughtful design: genuinely other, biologically coherent, psychologically derived, relatable enough to engage, and meaningful. Done well, aliens become memorable, believable, profound — among science fiction's most fascinating creations, expanding what life and mind can be while illuminating our own. Build aliens genuinely other, coherent, relatable, and meaningful.

Frequently asked questions

How do I write believable aliens?

Make them genuinely alien (truly other in psychology and nature, not "humans in rubber suits"), build coherent alien biology (a logical nature and environment from which their distinctiveness flows), derive their psychology from that nature (letting their biology and environment shape genuinely different minds), keep a thread of relatability (enough connection for readers to engage), and use them for theme and wonder. Coherent, genuinely-other, relatable aliens are believable.

What's the "humans in rubber suits" problem?

It's the classic alien failure — an extraterrestrial that looks different but thinks, behaves, and is essentially human, wasting the point of aliens (their otherness). A genuinely alien being is different at a deep level (in psychology, perception, values, biology), not just appearance. The fix is designing aliens with genuine, deep otherness derived from their nature, making them truly extraterrestrial rather than humans in disguise.

How do I make aliens feel genuinely other?

Derive their psychology from their nature — consider how beings with their specific biology, senses, environment, evolution, and society would think, perceive, value, and behave differently. Their different nature should produce genuinely different drives, ways of thinking, and worldviews, flowing logically from what they are. This deep otherness, rooted in coherent biology, makes aliens authentically other rather than humans with strange appearances.

Should aliens be relatable?

For aliens meant as characters readers connect with, yes — keep a thread of relatability (a relatable emotion or drive, a comprehensible goal, a point of connection) so readers can engage across the otherness. An alien so incomprehensible readers can't relate to anything fails to engage, unless true incomprehensibility is the point (a valid but difficult choice). Balance genuine otherness with a comprehensible bridge.

Related reading

• How to Write Nonhuman Characters
• How to Write Science Fiction
• How to Write Fantasy Creatures