Undernutrition, a chief child killer in developing countries, has been a major public health problem in Haiti. Following the 2010 disasters (earthquake and cholera) and the intensive relief efforts to address them, we sought to determine the trends of child undernutrition in Haiti using data from the 2005–06 Haiti Demographic and Health Survey (HDHS) and from a Standardized Monitoring and Assessment of Relief and Transitions (SMART) survey in 2012. Growth data analyses included 2,463 (HDHS) and 4,727 (SMART) children ages 0–59 months. We calculated the prevalence of stunting, wasting, and underweight for each survey using World Health Organization 2006 growth standards. To account for sampling design, probability weights were applied to all analyses. Statistical significance was determined by non-overlapping confidence intervals around estimates. Stunting prevalence declined from 28.5% (95% confidence interval [CI]?=?25.9, 31.3) in 2005-06 to 22.2% (95% CI?=?20.2, 24.3) in 2012; wasting, from 10.1% (95% CI?=?8.2, 12.7) to 4.3% (95% CI?=?3.6, 5.2); and underweight, from 17.7 % (95% CI?=?15.6, 20.1) to 10.5% (95% CI?=?9.3, 11.9). Additionally, stunting declined more in rural areas, from 33.6% (95% CI?=?30.1, 37.2) in 2005–06 to 25% (95% CI?=?23.4, 26.7) in 2012, than in urban areas, from 18.6% (95% CI?=?15.3, 22.5) in 2005–06 to 18.4% (95% CI?=?16.7, 20.1) in 2012, for reasons that remain unknown. Results of the 2012 HDHS confirmed the observed trends. Thus, undernutrition among Haitian children under 5 declined significantly between 2005–06 and 2012. Our results should be interpreted in view of investments and changes that occurred in different sectors (within and outside health and nutrition) before and after the earthquake.