Both child growth and dietary diversity are poor in rural Timor-Leste. The rainy season is associated with food scarcity, yet the association between seasonal scarcity, food diversity, and child growth is underdocumented. This study assesses the relationship between household dietary diversity and children's standardized growth across the 2018 food-scarce (April–May; post-rainy period) and post-harvest (October) seasons in the agricultural community of Natarbora, on the south-coastal plains of Timor-Leste. We conducted household interviews and collected anthropometric data across 98 and 93 households in the post-rainy and post-harvest periods, respectively. Consumed household foods were obtained via 24-h diet recalls and were subsequently categorized into a nine-food-group dietary diversity score (DDS; number of different food groups consumed). The DDS was related to children's standardized short-term growth (z-weight, z-body mass index [BMI] and percent change in weight over the harvest season) via linear mixed models. Across seasons, DDS increased from 3.9 (standard deviation [SD] = 1.0) to 4.3 (SD = 1.4; p < 0.05). In the post-rainy season, children in high DDS households had higher z-weight than those in low DDS households and higher z-BMI than children in medium and low DDS households. In the post-harvest period, household DDS did not predict children's z-weight but predicted z-BMI. Consumption of protein-rich foods, particularly animal-source foods and legumes, in low- and medium-DDS households may be associated with improved child growth. While consuming more animal-source foods in the post-rainy season would be ideal, promoting the consumption of locally grown legumes, such as beans and pulses, may facilitate better nutritional outcomes for more children in rural Timor-Leste.