Psychosocial factors have been found to relate to parental reflective functioning (PRF), a parent's ability to mentalize about themselves and their child. Relations between maternal psychosocial risk factors and PRF were investigated in a community sample. A sample of mothers (n = 146) was assessed for risk factors when infants were 6 months, infant temperament was assessed using an observational measure, and PRF was assessed with the Parent Development Interview-Revised (PDI). PRF was measured again with the Parental Reflective Functioning Questionnaire (PRFQ) when children were 4 years (n = 105) and 5 years (n = 92), with an additional sample of mothers (n = 48) tested at these two timepoints. Results showed that in infancy, total maternal psychosocial risk related to lower PDI-PRF; regression analyses highlighted low socioeconomic status, unplanned pregnancy, and low maternal anxiety as independent predictors of lower PDI-PRF. PDI-PRF scores at 6 months did not relate to PRFQ scores, but PRFQ subscales showed stability over time from age 4–5. Results are discussed with regard to the impact of maternal psychosocial risk and infant temperament on PRF and the stability and concordance of PRF measures.