In obsessive-compulsive disorder, reassurance seeking (RS) is associated with negative consequences for individuals who seek reassurance and their significant others. Reassurance seeking can be difficult to identify and treat, in part due to a lack of comprehensive assessment tools that can efficiently detect RS sought either overtly (i.e., obvious questions) or covertly (i.e., subtle attempts that are not direct questions), related to general threats (e.g., risks associated with stoves, locks) or social/relational threats (e.g., risks associated with relationship stability). Additionally, while the most commonly employed psychological treatment for RS entails strict refusal/withdrawal of accommodation to RS, this intervention may be associated with low acceptability. Conversely, a novel intervention wherein partners provide support to encourage tolerating distress may effectively reduce RS while being more acceptable to those who would receive it. This program of research was designed to address these gaps regarding assessment of and intervention for problematic RS. Study 1 entailed the validation and psychometric analysis of a novel measure of RS, the Covert and Overt Reassurance Seeking Inventory (CORSI), which assesses general and social/relational threat-motivated RS sought covertly or overtly. Results from undergraduate validation (N = 1621) and clinical (collapsed N = 140) samples suggested that the CORSI has a five-factor structure, sound psychometric properties, and can effectively discriminate RS of those with and without mental disorders. Study 2 entailed an experimental manipulation of partners’ feedback to correspond with support provision or traditional accommodation reduction in response to undergraduate participants’ (N = 102) RS following a threat-inducing task. Overall, support provision was associated with significantly greater ratings of helpfulness and a trend towards less overall RS. In Study 3, undergraduate participants and familiar partners (N = 179) provided ratings of perceived treatment acceptability/endorsement and selected which intervention they would prefer by reading vignette descriptions of RS interventions based on traditional accommodation reduction or support provision. Results indicated that participants and their partners provided more favourable ratings of acceptability/endorsement for the support provision intervention and were significantly more likely to select it than strict accommodation reduction. The implications of these findings for research and clinical practices are discussed.