This study assessed the effect of two capacity-building constructs, namely Teacher Training Programs and Professional Development Workshops, on the performance of public Early Childhood Development and Education (ECDE) teachers in Changamwe Sub-County, Mombasa County, Kenya. The study was anchored on Human Capital Theory, which explains how deliberate investment in employees' knowledge and skills translates into improved job performance. A descriptive research design was adopted, and a census approach was used to target all 80 ECDE teachers in Changamwe Sub-County. Following a pilot study involving eight teachers, seventy-two questionnaires were administered, of which fifty-five were returned, representing a response rate of 76%. Data were collected using structured, five-point Likert-scale questionnaires whose reliability was confirmed through Cronbach's alpha values of 0.76 for teacher training programs and 0.85 for professional development workshops, both exceeding the recommended 0.70 threshold. Data were analysed using descriptive statistics, Pearson correlation, and multiple linear regression with the aid of SPSS. The findings revealed that teacher training programs had a moderate, positive correlation with teacher performance (r = 0.473, p < 0.01) but a statistically insignificant regression effect (β = 0.104, t = 1.761, p > 0.05), suggesting that formal training plays a largely indirect role in shaping day-to-day teaching performance. Professional development workshops, on the other hand, recorded a weaker but statistically significant correlation with performance (r = 0.289, p < 0.01) and a strong, statistically significant regression effect (β = 0.389, t = 6.516, p < 0.01), confirming workshops as a key driver of instructional effectiveness. The study concluded that while both constructs are positively regarded by teachers, professional development workshops exert a more direct and statistically significant influence on teacher performance than formal training programs. The study recommends that education authorities in Mombasa County increase the frequency of context-specific training sessions linked to actual classroom practice, and that professional development workshops be designed around hands-on, collaborative, and peer-to-peer learning to sustain their demonstrated impact on teacher performance.