Background Primary health care (PHC) was a keystone toward achieving universal health coverage and Sustainable Development Goals (SDGs). China has made efforts to strengthen its PHC institutions. As part of such efforts, regular in-service training is crucial for primary healthcare workers (PHWs) to strengthen their knowledge and keep their skills up to date. Objective To investigate if and how the existing training arrangements influenced the competence and job satisfaction of PHWs in township hospitals (THs). Methods A mixed method approach was employed. We analyzed the associations between in-service training and competence, as well as between in-service training and job satisfaction of PHWs using logistic regression. Interviews were recorded, transcribed, and analyzed using NVivo12 to better understand the trainings and the impacts on PHWs. Results The study found that training was associated with competence for all the types of PHWs except nurses. The odds of higher competence for physicians who received long-term training were 3.60 (p < 0.01) and that of those who received both types of training was 2.40 (p < 0.01). PHWs who received short-term training had odds of higher competence significantly (OR = 1.710, p < 0.05). PHWs who received training were more satisfied than their untrained colleagues in general (OR = 1.638, p < 0.01). Specifically, physicians who received short-term training (OR = 1.916, p < 0.01) and who received both types of training (OR = 1.941, p < 0.05) had greater odds of general job satisfaction. The odds ratios (ORs) of general job satisfaction for nurses who received short-term training was 2.697 (p < 0.01), but this association was not significant for public health workers. The interview data supported these results, and revealed how training influenced competence and satisfaction. Conclusions Considering existing evidence that competence and satisfaction serve as two major determinants of health workers' performance, to further improve PHWs' performance, it is necessary to provide sufficient training opportunities and improve the quality of training.