Purpose <p>Thought disorder (TD) is a complex constellation of experiences often manifested as disorganised speech. While both social isolation and delusions have been independently linked to TD, little is known about how these factors may interact. This study investigated whether social isolation and delusions predict the disorganised dimension of TD and whether delusions moderate the association between social isolation and disorganisation, controlling for relevant covariates.</p> Methods <p>Data from two clinical samples of individuals diagnosed with psychotic-spectrum disorders were combined (<i>n</i> = 148). Participant speech samples were transcribed and scored using the Thought, Language, and Communication (TLC) scale. Factor analysis identified key components of TD. Moderation analyses using linear regression examined whether delusions moderated the relationship between social isolation and disorganisation, controlling for covariates.</p> Results <p>Both social isolation and delusions independently predicted TD disorganisation. Moderation analyses revealed that delusions significantly amplified the association between social isolation and disorganisation, particularly at moderate-to-high levels of delusional severity. The model accounted for approximately 40% of variance in disorganisation.</p> Conclusion <p>Findings indicate that delusions moderate the impact of social isolation on the disorganisation factor of TD. This underscores the importance of integrated interventions that target both social connectivity and delusional symptoms to improve communicative functioning in individuals with psychotic-spectrum disorders.</p>