Valentine is first introduced as a non-player character in the 2015 role-playing video game Fallout 4, where he plays an important role in its main plotline by lending his assistance to the search for the abducted son of the game's player character, the sole survivor of a cryogenics-focused facility designed to withstand nuclear fallout built by a technology company known as Vault-Tec.

With cracked synthetic skin torn in spots which expose the metallic structures underneath, Valentine is a type of sophisticated biomechanical android characters in Fallout 4 called "Synths".

Nick Valentine is very well received by video game publications and players, being widely regarded as one of the best remembered features from Fallout 4, as well as one of the most popular sidekick type characters in the series overall.

Originally intended to be discarded, Valentine survived his decommissioning with the memories of his namesake, a police detective who lived in Chicago and Boston, intact.

[2] Valentine eventually came to terms with who he is, accepted the role his memories played in shaping his own personality, and decided to work as a professional private investigator.

He started dressing up like an archetypal "gumshoe", a slang term for a stereotypical private detective who wore street shoes with a thick, soft and quiet rubber sole.

[6] A "unique, advanced second-generation synth model", Valentine's mannerisms and personality was envisioned to be a firmly "noirish vibe", with concept art depicting him smoking a cigarette, and wears a trilby hat and trenchcoat.

[3] As part of the main storyline of Fallout 4, the player character is advised to seek out Nick Valentine in Diamond City, to locate their son.

He suggests a trip to a nearby settlement called Goodneighbor to speak to Doctor Amari, who works at a place known as the Memory Den, to extract information about the Institute from Kellogg's brain.

[14] Shacknews named Valentine one of the best characters of 2015 for their year end review, praising the "juxtaposition between his noir roots and sci-fi setting", his integral contributions to the main plot by helping to bring the game into focus, as well as his personal story arc.

[13][16] Through the backstory of how he came to wear his signature hardboiled detective’s outfit, Joseph Knoop from Game Informer highlighted Nick Valentine as an exemplar of what it means to feel “right” within a new world, and how appearances can impact that.

[3] Meer likened his personality, an "innate, obvious tenderness and warmth that isn't undermined by shooting raiders and mutants", to that of an archetypal loving grandfather's.

[3] Meer emphasized that Valentine's kind demeanor and unique perspective on the game's events stood out for him and many others in spite of the limited party management and dialogue in Fallout 4 or its technical issues, not because of it.

Thier found that not only is the culmination of his side quest to settle a personal score poignant, it also compliments the game's essential "do robots have souls" theme.

[18] Miranda Sanchez from IGN praised Valentine's built-in ability to unlock most doors and security terminals for her using his hacking skill as convenient.