Background: In Malaysia, the rates of mothers practising breastfeeding exclusively among babies at six months of age still do not achieve the Global Nutritional Targets 2025 which is 50%. Objective: To determine the effectiveness of breastfeeding intervention in improving breastfeeding outcomes. Method: A quasi-experimental design was used involving a purposive sample of 96 primigravidas (intervention group (IG) = 48, control group (CG) = 48) recruited at Hospital USM. Data were collected using the Breastfeeding Assessment Questionnaire. Mothers in IG received the current usual care and two hours of an additional education programme on breastfeeding, breastfeeding booklet, notes from the module, and postnatal breastfeeding support in the first week of postpartum. Mothers in CG received the current usual care only. The mothers were assessed on the first and sixth week and then the fourth and sixth month of postpartum. Results: The results indicated that there was a statistically significant difference between the groups on the fourth month postpartum (X2 = 5.671, P = 0.017) in practicing full breastfeeding. The breastfeeding duration rates of the IG were longer than those of the CG. However, the results showed only two follow-up weeks that were significant (week 6, X2 = 5.414, P = 0.020, month 4, X2 = 7.515, P = 0.006). There was a statistically significant difference between IG and CG as determined by one-way ANCOVA on the breastfeeding duration after controlling age and occupation, F (3, 82) = 6.7, P = 0.011. The test revealed that the breastfeeding duration among IG was significantly higher (20.80 ± 6.31) compared to CG (16.98 ± 8.97). Conclusions: Breastfeeding intervention can effectively increase breastfeeding duration and exclusivity outcomes among primiparous mother