Purpose Achieving optimal nutrition among mothers and children is still a challenge in many developing country settings, including Ethiopia. Study on dietary diversity concordance of mother-to-child dyads is limited. Hence, this study aims to assess dietary diversity concordance among mother-to-child pairs and its associated factors in Gedeo zone, Southern Ethiopia. Design/methodology/approach A community-based cross-sectional study was carried out in Gedeo zone, South Ethiopia, from January 1 to February 15, 2019. A multistage sampling technique was used to select study participants. Data was collected by using a pretested and structured questionnaire. Data entry and analysis were done by Epi data version 3.1 and SPSS version 23.0 software, respectively. Bivariate and multivariate logistic regression models were used. Variables with p < 0.25 at bivariate analysis were chosen for multivariate analysis. Variables with a p-value of <0.05 were considered statistically significant. Findings A total of 665 mother and child dyads participated, with a response rate of 98.6%. High concordance of dietary diversity among mother-to-child pairs was 9%. Age of the mother (adjusted odds ratio [AOR] = 0.21; 95% confidence interval [95% CI]: 0.05–0.84), age of the child between 6 and 11 months (AOR = 5.2; 95% CI: 2.3–11.6), being female (AOR = 1.8; 95% CI: 1.0–3.4), previous history of infection (AOR = 4.4; 95% CI: 1.8–11.5), source of food from the market (AOR = 0.34; 95% CI: 0.12–0.81) and rich wealth index (AOR = 5.7; 95% CI: 2.5–12.9) were the significant factors of high concordance of dietary diversity. Originality/value The prevalence of high-concordant dietary diversity among mother and children dyads was very low. Therefore, ensuring multisectoral nutrition interventions that focus on both mothers and children should be considered to improve the good dietary diversity practice.