Autistic individuals have reported lower satisfaction in their romantic relationships compared to non-autistic individuals. Previous research on the factors that contribute to relationship satisfaction within autism has focused on the characteristics of autistic participants as barriers to relationship satisfaction, while overlooking the role of their partners. This study investigated a range of factors and their association with long-term relationship satisfaction for 95 autistic individuals and 65 non-autistic individuals in current or previous long-term relationships with autistic individuals. Participants completed an online survey, including questionnaires measuring autistic traits, the Big Five personality traits, social loneliness, partner responsiveness, sexual satisfaction and relationship satisfaction. Partner responsiveness significantly predicted relationship satisfaction for both autistic and non-autistic partners. The findings suggest that to enhance relationship satisfaction, service providers working with couples involving an autistic individual would improve the relationship by focusing on assisting their clients to identify each other's needs and how best to meet them.