Introduction Infants with low body weight (LBW) are major challenges for post cardiac surgery care. We conducted this study to compare post-operative course and outcome of infant weighing 2.2kg or less with matching group of infants with normal body weight who underwent similar cardiac surgery. Methods We reviewed retrospectively all infants below 2.2kg who underwent cardiac operation at our institution from January 2001 to March 2011. Cases with LBW (group A) were compared with matching group (group B) of normal body weight infants who had similar cardiac surgery and matching surgical risk category. We compared demographic, ICU parameters, complications and short-term outcome of both groups. Results Thirty seven patients were included in group A and 39in group B. Except for Weight (2.13±0.08kg in group A vs. 3.17±0.2kg in group B); there was no statistical difference in demographic data between both groups. Cardiac procedures included coarctation repair, Arterial switch, VSD repair, tetralogy of Fallot repair, systemic to pulmonary shunt and Norwood procedures. Patients in group A had statistically significant difference from group B in term of bypass time (p=0.01), duration of inotropes (p=0.01), duration of mechanical ventilation (p=0.004), number of re-intubations (p=0.015), PCICU length of stay (p=0.007) and mortality (13.5% in group A vs. 0% in group B, p value 0.02). Conclusion Patients with LBW below 2.2kg can go for cardiac surgery with overall satisfactory result but with increase risk of ICU morbidity and mortality.