Malaria is a major public health problem and cause of suffering and premature death in tropical and subtropical countries. The population groups considered to be at a higher rate of contracting malaria and developing severe include infants, children under 5 years of age, pregnant women and patients with HIV/ AIDS, non-immune migrants, mobile populations and travelers. There is a need for constant research to be carried out to evaluate the prevalence. This study determined malaria infection among under-fives and mothers aged 8- 40 years that attended Model Primary Health Centre, Ozuoba, Rivers State, Nigeria between 2016- 2020. Records with medical diagnoses of all the children (0 – 5) years and mothers aged 18- 40 years that attended the health facility during the specified period were collected and analyzed. Data were analyzed with logistic regression, frequency, mean, standard deviations, and percentages using SPSS version 21.0 statistical software. The result of this study revealed an overall malaria infection rate of 46.7% for the under-fives and 35.4% for the mothers. Yearly infection rates of malaria among the studied groups were from 44% to 59%, within the five years studied. The highest infection rate (58.6%) for malaria in the under-fives occurred in 2016 and for the mothers, the highest (44.6%) was in 2019. Age was found to be a significant factor for malaria infection (p< 0.0001, χ2=434.3) among the studied under-fives. The ≥12 months old had less malaria infection rate (38.5%) while 48 months (4years) had the highest rate of infection (56.8%). Sex of the under-fives did not have significant impact on malaria infection rate (p = 0.205, χ2=1.606). Mothers’ age showed significant association with malaria infection (p = 0.006, χ2=12.597), with mothers 31 - 35years recording higher infection rate (37.7%) than those of 18-25 years old (30.8%). The education level of mothers also influenced infection rate (p = 0.0001, χ2=10.388) as those with tertiary education had the highest rate (38.9%) compared to those of secondary and primary levels at 36.8% and 36.7% respectively. The occupation of mothers was also found significant (p = 0.0001, χ2=25.585) with malaria infection being highest among farmers (44.4%), but lowest with students (29.7%).The results of this study showed a very high prevalence of malaria infection among the most vulnerable, and hence the need for improved access to all malaria interventional measures like quality and affordable malaria drugs and insecticide-treated nets.