The present study was assess the pre-test knowledge, evaluate the effectiveness of a structured – teaching program on the influence of maternal diet and associate post-test knowledge with the selected demographic variables. The study was used a pre– experimental one group pretest –post-test research design. The sample size was 20 selected by convenience sample technique, primi mother admitted in MAPIMS, Melmaruvathur. Pre test knowledge was assessed, provide structured- teaching program and after assessed post test knowledge on maternal diet. There was a statistically significant difference between pretest and posttest mean knowledge score with the “t” value 29.82 at <0.000 level of significance. Hence structured teaching program on maternal diet was effective in increasing the knowledge among primi lactating mothers.