en <span style=font-size:14px;><span style=unicode-bidi:embed><span new= roman= style=font-family: times=><b><span cambria= style=font-family:>Aims:</span></b><span cambria= style=font-family:> Appropriate complementary feeding is one of the main ways to prevent malnutrition in infants, which is a serious health problem in developing countries including Iran. This study aimed to investigate the effectiveness of a theory-based educational intervention on timely complementary feeding initiation in primiparous mothers. </span></span></span><br> <span style=unicode-bidi:embed><span new= roman= style=font-family: times=><b><span cambria= style=font-family:>Materials & Methods</span></b><b><span style=background:white><span cambria= style=font-family:><span style=color:#000033>:</span></span></span></b> <span cambria= style=font-family:>In this randomized controlled trial, 68 primiparous mothers (34 in each intervention and control group) of infants aged 2 to 3 months participated in the study using a Multi-stage random sampling method in Kashan, Iran, 2019. The educational intervention was designed based on the theory of planned behavior. The data collection tool included a demographic information questionnaire and a researcher-made questionnaire designed based on the theory of planned behavior. SPSS 22 software was used for data analysis, using Chi-square test, independent and paired t-test. Statistical significance was set at p<0.05. </span></span></span><br> <span style=unicode-bidi:embed><span new= roman= style=font-family: times=><b><span cambria= style=font-family:>Findings: </span></b><span cambria= style=font-family:>After the intervention, there were significant increases in the mean scores of knowledge (p=0.004) and attitude (p=0.02) in the intervention group compared to the control group, but the mean scores of intentions to initiate complementary feeding timely, showed no significant differences between the control group and the intervention group. A significant increase was seen in the mean score of perceived behavioral control in the intervention group (p=0.002). Only perceived behavioral control significantly increased the chances of timely initiation of complementary feeding (OR=1.36, p=0.002). </span></span></span><br> <span style=unicode-bidi:embed><span new= roman= style=font-family: times=><b><span cambria= style=font-family:>Conclusion:</span></b><span cambria= style=font-family:> The educational programs based on the theory of planned behavior has small effects on improving timely complementary feeding.</span></span></span></span> Complementary Feeding, Behavior , Children 75 81 http://hehp.modares.ac.ir/browse.php?a_code=A-10-63762-1&slc_lang=en&sid=4