Pharmaceutical care is an essential component of mental healthcare. The study assessed pharmacists' collaborations, barriers, perceptions on therapeutic relationships and attitudes toward pharmaceutical care to persons with mental illness. A questionnaire-based descriptive cross-sectional survey was conducted among 175 pharmacists in a Nigerian state via purposive sampling. Average mean score of >3 (±SD) was considered positive attitude toward pharmaceutical care, and positive for respondents' perception of pharmacists-patient relationship during consultations. Data were analyzed using SPSS version 25.0 for descriptive statistics. A total of 140 (80.0%) respondents participated in the study. Access to patients' medical records 90 (64.3%) was the major barrier to the provision of pharmaceutical care to persons with mental illness. Almost half of the study participants 69 (49.3%) desired collaboration with only general practitioners and psychiatrists. Only 44 (31.4%) had full co-operation from their desired collaborators. Average score for respondents' attitude toward provision of pharmaceutical care to the patients, and perception of pharmacist-patient relationship were 4.5 (±0.7) and 3.8 (±0.9) respectively. Study participants' attitude toward pharmaceutical care, and perception on therapeutic relationship in persons with mental disorder were positive. Lack of access to patients' records mostly hindered provision of pharmaceutical care, and full collaboration with other mental health experts was mostly lacking. Appropriate policies are required to improve these vital components of mental healthcare for desired outcomes.