Training and development are important human-resource practices through which organisations seek to improve employee knowledge, skills, competencies and performance. However, the existence of training programmes does not necessarily guarantee improved employee performance, particularly where training is poorly aligned with employee needs or workplace requirements. This study examined the effects of training and development on employee performance in selected Local Government Areas in Oyo State, Nigeria. Specifically, the study assessed the individual effects of off-the-job training, on-the-job training, mentoring and coaching on employee performance and determined their joint effect. A quantitative descriptive survey design was adopted. The study covered five purposively selected Local Government Areas representing the five administrative zones of Oyo State. The population comprised senior staff on Grade Levels 12–17, while a sample of 260 respondents was selected through multi-stage sampling involving purposive, proportionate and simple random sampling techniques. Primary data were collected using a structured questionnaire measured predominantly on a five-point Likert scale. Descriptive statistics, simple linear regression and multiple linear regression were employed for data analysis, with hypotheses tested at the 5% significance level. The results showed generally favourable perceptions of the training and development dimensions, with mean scores of 3.865 for off-the-job training, 3.855 for on-the-job training, 3.927 for mentoring and 3.856 for coaching, while employee performance recorded a mean of 3.775. However, inferential results showed that off-the-job training had a positive but insignificant effect on employee performance (β = 0.080, p = 0.176). On-the-job training also had a positive but insignificant effect (β = 0.091, p = 0.137), while mentoring had an almost zero and insignificant effect (β = −0.003, p = 0.966). Coaching similarly had a positive but insignificant effect (β = 0.045, p = 0.445). The joint regression model was also insignificant (R = 0.130, R² = 0.017, F = 1.125, p = 0.345), indicating that the four dimensions jointly explained only 1.7% of the variation in employee performance. The study concludes that although training and development activities were favourably perceived, they did not independently or jointly produce statistically significant effects on employee performance in the selected Local Government Areas. It recommends systematic training-needs assessment, improved relevance and quality of training programmes, stronger post-training follow-up, structured mentoring and coaching, effective training evaluation, and greater organisational support for applying acquired skills.