Seeking professional help for mental illness is a limited practice among Black family members in low and middle socioeconomic groups in the United Kingdom (UK) and Nigeria. Guided by the theory of planned behavior, we explored some factors restricting professional help-seeking practices among the target groups. This mixed-methods study recruited a heterogeneous sample of 105 ( ranging from 19–64 years) UK and Nigerian Black family members in low or middle socioeconomic groups. Data were collected using a standardized questionnaire and open-ended questions. Collected data were analyzed using IBM SPSS statistics (version 22.0) and thematic analysis. There was no statistically significant difference in professional help-seeking behavior among the UK and Nigerian Black family members in low and middle socioeconomic groups [
F
(3, 83) = 1.13;
p
> .05]. The qualitative data analysis revealed that respondents were limited from professional help-seeking due to high consultation fees to see a mental health professional, perceived accessibility to mental health services within their various locations, stigmatization and socio-cultural factors (such as, “The perception that a man should be strong” or “Mental health isn’t as important as physical health”), concerns about the safety of information shared during professional help-seeking or therapy sessions, poor knowledge about mental health services, long waiting time to see a professional in face-to-face therapy, and risk of contracting the infectious disease in the hospital setting. Implications of findings for theory and practice and direction for future research are thus discussed.