Background: Complementary feeding is a process that begins when breast milk alone is no longer sufficient to meet the nutritional needs of the baby and, as a result, other foods are needed in addition to breast milk. The aim of this study was to assess the pre- and post- test knowledge and attitudes of the infant's mother and to determine the effectiveness of the self-instructional module for knowledge and attitudes and to determine the relationships between pre-test knowledge with their selected demographic variables.

Methods: This is a Quantitative Pre-experimental, One-group pre-test post-test design research with the sample size of 152 mothers of infants from aged 4-6 months who were selected using non-probability purposive sampling from Gangtok, East Sikkim. Data was collected through demographic proforma, Semi-structured knowledge questionnaire and 5-point Likert scale for which validity and reliability was established and self-instructional module on complementary feeding was provided to mothers of infants.

Result: In Pre-test 96(63.2% poor knowledge, 54(35.5%) average knowledge and only 2(1.3%) had good knowledge where as in post-test majority 133(87.5%) had good knowledge, 19(12.5%) had average knowledge and in Pre-test level of attitude majority 136(89.5%) had positive attitude and 16(10.5%) had negative attitude and in post-test 152(100%) had positive attitude towards complementary feeding and for finding the effectiveness of self-instructional module on knowledge and attitude mean post-test score of mothers were greater than the table value which was found statistically highly significant at p<0.05 level and also there was significant association between demographic variables such as educational qualification and monthly income of mothers at p<0.05 level of significance.

Conclusion: The study findings showed that Self-instructional module was effective in improving the knowledge and attitude regarding complementary feeding among mothers. Various teaching programmes can also be conducted for the mothers regarding complementary feeding to increase their knowledge at both hospital and community settings.