Despite the clear existing theoretical links, ours is the first direct systematic series of studies investigating a potential negative association between Honesty-Humility and general dishonesty in romantic relationships. Eleven preregistered online studies with community samples were run (total N = 5,677). For a first test of our hypothesis, we conducted a series of seven cross-sectional studies based on self-reports; these studies used different methodological approaches to assess relationship-based dishonesty (i.e., closed-ended self-report scales, scenarios, and direct frequency measures). This was followed by one diary study and three studies that base their assessment on more behavioral measurements of relationship-based dishonesty (e.g., a dice roll task and an anagram task). In line with our hypothesis, all studies reliably revealed that participants higher in Honesty-Humility reported less relationship-based dishonesty. The classification of the found results to past research and the general relevance of the Honesty-Humility factor for romantic relationships are discussed. (PsycInfo Database Record (c) 2023 APA, all rights reserved).