The rate of influencer marketing in Nigeria may allow for the proliferation of misinformation, especially in health-related areas where misleading information can pose significant risks to public health. This however, necessitated the investigation. The source credibility, and social influence theories guided the study. Survey research design was adopted. The study’s population was 974, 865, from which a sample size of 384 was determined using the smart survey sample size calculator. The multistage sampling technique was used with questionnaire as the instrument for data collection. Results showed that 39% of the respondents come across health and fitness posts promoted by micro influencers on social media very often. At a mean of 3.1, the majority of the respondents have a favourable and positive perception towards micro influencers’ advertisement of health and fitness brands. Micro influencers’ advertisement of health and fitness products have been effective in aiding the choice of health and fitness brands among the respondents at a mean score of 2.8. Also, reliability, authenticity and credibility of the influencer, testimonials, positive online reviews, influencers' trustworthiness, and content relevancy were some of the factors that induce the patronage of health and fitness brands advertised by micro influencers. It was concluded that, micro influencers’ followers can convincingly accept health and fitness brands recommended by these influencers because they believe them to be credible. Amongst others, it was recommended that, health and fitness brands should always continuously prioritise partnerships with credible, trustworthy, and reliable micro health influencers who align closely with brand values.