Primary health care workers are central to delivering essential public health functions (EPHFs), yet gaps in their knowledge, attitudes, and practices can compromise service effectiveness. This study assessed the knowledge, attitudes, and practices of EPHFs among primary health care workers in Port Harcourt Local Government Area, Rivers State, Nigeria, and identified factors influencing their implementation. A cross-sectional census of all 153 primary health care workers in government-owned facilities was conducted using a structured questionnaire. Knowledge was categorised as good (5-7), fair (4), or poor (0-3). Attitudes and practices were categorised as positive/good (≥3.67), neutral/fair (2.34-3.66), or negative/poor (≤2.33). Data were analysed using descriptive statistics, chi-square tests, and multivariate logistic regression at p < 0.05. Response rate was 100%. Respondents were predominantly female (73.2%), with mean age 36.4 ± 8.7 years. Only 46.4% had received training on EPHFs, 55.6% had access to guidelines, and 51.0% received regular supervision. Overall, 87.0% had adequate knowledge (good + fair), with a mean score of 5.89 ± 1.24 out of 7. Knowledge was highest for immunisation (92.2%) and lowest for monitoring and evaluation (77.8%). Most respondents (89.5%) held positive attitudes (grand mean 4.35 ± 0.58). The lowest attitude score was for training preparation (3.95). For practice, 67.3% demonstrated good practice (grand mean 3.98 ± 0.78). The lowest practice score was for programme planning and evaluation (3.62). Years of experience was significantly associated with knowledge (χ² = 14.28, p = 0.006). Training was the strongest predictor of adequate knowledge (AOR = 5.89), positive attitude (AOR = 4.12), and good practice (AOR = 3.56). Guideline availability predicted all three outcomes, while supervision predicted good practice alone (AOR = 2.14). While most workers possess adequate knowledge and positive attitudes, significant gaps exist in practice. Training, guideline availability, and supervision require urgent strengthening.

Keywords: Essential Public Health Functions (EPHFs), Primary health care workers, Knowledge, Attitude, Practice.