(1) Hearing health training and promotion is a priority for early childhood development (ECD) practitioners, but training opportunities are limited, especially in low- and middle-income countries (LMIC). mHealth (mobile health) has the potential to deliver scalable ear and hearing training to ECD practitioners. (2) This study investigated the effect of an mHealth training intervention program for ECD practitioners to improve knowledge and perceptions of hearing health in young children. An experimental one-group, pre-post-test study included ECD practitioners working with children between birth and 6 years old across 31 neighbouring communities in the Western Cape Province, South Africa. Hearing health training was provided using WhatsApp messages that encompassed infographics and voice notes. Knowledge and perceptions regarding hearing and hearing-related problems in children were surveyed pre-training, directly post training, and 6 months post training. (3) ECD practitioners (N = 1012) between 17 and 71 years of age received the mHealth training program and completed both the pre-and post-training surveys. Overall, knowledge scores indicated a significant improvement from pre- to post training (Z = −22.49; p < 0.001). Six-month post-training knowledge scores were sustained. Content analysis of ECD practitioners’ application of the training information 6 months post training indicated improved awareness, practical application, better assistance for hearing problems, and widespread advocacy. (4) The mHealth training program supports improved knowledge and perceptions of ECD practitioners regarding hearing health for young children. With improved knowledge scores maintained 6 months post training, mHealth hearing health training is an effective intervention. An mHealth training program for ECD practitioners provides a scalable, low-cost intervention for primary and secondary prevention in childhood hearing loss, especially in LMICs.