Ruth Rendell Mysteries includes LGBTQ+ characters, whose identities are typically incidental to the overarching crime narratives. The portrayal generally avoids strong positive or negative arcs, presenting queer individuals as part of the complex human landscape without significant affirmation or denigration, thus resulting in a neutral net impact.

The series features a transsexual character in 'The New Girlfriend' episode whose identity is a central secret. Its revelation leads to a tragic and punitive outcome for the character, highlighting societal prejudice and the devastating consequences of non-acceptance without a strong counter-narrative affirming trans lives. The portrayal leans negative due to the unrelieved misery and fatal outcome.

The series often explores the darker aspects of human psychology, where Christian adherence is occasionally depicted as a facade for hypocrisy, repression, or moral rigidity that contributes to characters' psychological dysfunction or criminal behavior. The narrative frequently exposes the gap between outward piety and inner corruption without consistently offering counterbalancing portrayals of faith as a genuine source of virtue or comfort.