Background: Monitoring urinary iodine concentration (UIC) after sustained exposure informs iodine delivery strategies. We aimed to compare endline UIC among women of reproductive age (WRA) and preschool children (PSC) receiving multiple micronutrient-fortified (MMF) vs. iodine-only bouillon, and to describe population iodine status at baseline and endline. Methods: This pre-specified secondary outcome analysis used Condiment Micronutrient Innovation Trial (CoMIT) data. Non-pregnant, non-lactating WRA (15-49 years) and PSC (2-5 years) were enrolled at the household level. Households received MMF or iodine-only bouillon for 9 months (38 weeks); both contained iodine (KIO3) at 30 ug/g. Baseline and endline UIC (ug/L) were measured by modified Sandell-Kolthoff reaction in spot urine samples. ANCOVA models, adjusted for baseline log-UIC and recruitment site, compared endline geometric mean UIC between trial arms. Median UIC at both timepoints was compared to WHO cut-offs (ug/L): =300 (excessive); the prevalence of UIC