Integrating small-quantity lipid-based nutrient supplements (SQ-LNS) into infant and young child feeding (IYCF) programmes can increase consumption of essential nutrients among children in vulnerable populations; however, few studies have assessed the impact of integrated IYCF-SQ-LNS programmes on IYCF practices. A 2-year, enhanced IYCF intervention targeting pregnant women and infants (0-12 months) was implemented in a health zone in the Democratic Republic of Congo (DRC). The enhanced IYCF intervention included community- and facility-based counselling for mothers on handwashing, SQ-LNS, and IYCF practices, plus monthly SQ-LNS distributions for children 6-12 months; a control zone received the national IYCF programme (facility-based IYCF counselling with no SQ-LNS distributions). Cross-sectional preintervention and postintervention surveys (n = 650 and 638 in intervention and control areas at baseline; n = 654 and 653 in each area at endline, respectively) were conducted in mothers of children 6-18 months representative of both zones. Difference in differences (DiD) analyses used mixed linear regression models. There were significantly greater increases in the proportion of mothers in the intervention (vs. control) zone who reported: initiating breastfeeding within 1 hr of birth (Adj. DiD [95% CI]: +56.4% [49.3, 63.4], P < 0.001), waiting until 6 months to introduce water (+66.9% [60.6, 73.2], P < 0.001) and complementary foods (+56.4% [49.3, 63.4], P < 0.001), feeding the minimum meal frequency the previous day (+9.2% [2.7, 15.7], P = 0.005); feeding the child in a separate bowl (+9.7% [2.2, 17.2], P = 0.01); awareness of anaemia (+16.9% [10.4, 23.3], P < 0.001); owning soap (+14.9% [8.3, 21.5], P < 0.001); and washing hands after defecating and before cooking and feeding the child the previous day (+10.5% [5.8, 15.2], +12.5% [9.3, 15.6] and +15.0% [11.2, 18.8], respectively, P < 0.001 for all). The enhanced IYCF intervention in the DRC was associated with an improvement in several important IYCF practices but was not associated with a change in dietary diversity (minimum dietary diversity and minimum acceptable diet remained below 10% in both zones without significant differences between zones). The provision of fortified complementary foods, such as SQ-LNS, may be an important source of micronutrients and macronutrients for young children in areas with high rates of poverty and limited access to diverse foods. Future research should verify the potential of integrated IYCF-SQ-LNS to improve IYCF practices, and ultimately children's nutritional status.