Clinical outcomes after a first-episode of psychosis (FEP) are heterogeneous. Many patient-related factors such as gender and comorbidity have been studied to predict symptomatic outcomes. However, psychiatrist-related factors such as prescription behaviour and gender have received little attention. We assessed the relationship between patients’ psychiatrists, psychosis severity and daily functioning in 201 patients remitted from an FEP for a duration of one year, treated by 18 different psychiatrists. We controlled for baseline severity, dose and type of antipsychotic medication, frequency of visits, and patients’ education. Symptom severity, daily functioning, and antipsychotic drug use were assessed at baseline and at 3, 6, and, 12 months follow-up. We found that psychiatrists accounted for 9.1% of the explained variance in patients’ symptom severity and 10.1% of the explained variance in daily functioning.These effects persisted even when controlling for factors such as baseline severity and the prescribed dose. The effect of prescribed dose on symptom severity and daily functioning differed between psychiatrists. Treatment centre, session frequency, and medication nonadherence were not related to symptom severity. Our results emphasize the importance of individual psychiatrist factors in symptomatic outcomes after an FEP. Further identification of psychiatrist-related factors such as the quality of therapeutic alliances and shared decision-making, may optimize psychiatrists’ training with the goal of improving patient outcomes.