In a sample of outpatients (152 females, 152 males) receiving individual provider-initiated HIV testing and counselling (PITC) we aimed to identify factors associated with subsequent uptake of partner HIV testing. Purposively sampled outpatients receiving PITC at a Ugandan hospital completed a questionnaire immediately prior to testing for HIV, and then at 3 and 6 months post-test. By 6-month follow-up 96% of participants reported disclosing their HIV test results to their partner and 96.4% reported asking their partner to test. 38.8% of women and 78.9% of men reported that their partner tested and they knew their results. Recent (men: AOR 5.84, 95.0% CI 1.90–17.99; women AOR 6.19, 95.0% CI 2.74–13.59) or any previous testing by the partner (women: AOR 4.01, 95% CI 1.06–15.10) predicted uptake of partner testing by the 6-month follow-up. Among women, perceiving greater social support from their partner, which perhaps reflects better relationship quality, was predictive of their male partner testing for HIV (AOR 2.37, 95% CI 1.22–4.58). Notably intimate partner violence showed no negative association with partner testing. Our findings demonstrate that women are at a disadvantage compared to men in their ability to influence their partner to test for HIV, and that improving social support in intimate relationships should be a focus of HIV partner testing interventions. However, more research on interventions to improve partner testing is needed, particularly in identifying effective ways to support women in engaging their partners to test.