Pak-choi is one the most important leafy vegetables, which is extensively grown and consumed in Cambodia. Insect pests, especially lepidopteran caterpillars and the flea beetles are one of the major production constraints in pak-choi. This has forced the vegetable farmers to heavily rely on calendar-based application of chemical pesticides. In order to develop an effective alternative to harmful pesticides, we evaluated the effectiveness of microbial pesticides (Bacillus thuringiensis and Metarhizium anisopliae formulations), and neem leaf extract alone and in combination (as an IPM package) against diamondback moth, common armyworm, cabbage webworm and striped flea beetle on pak-choi in three different provinces of Cambodia during 2015-early 2018. Bacillus thuringiensis and M. anisopliae formulations reduced the incidence of diamondback moth, common armyworm, cabbage webworm and the damage by striped flea beetle to the levels equivalent to chemical pesticide (abamectin). Yield was significantly higher in bio-pesticide treated plots than untreated plots in most of the trials. The performance of the IPM package was on par with Farmers’ practice (calendar-based application of chemical pesticides) in reducing the damage by target pests, leading to significantly higher yield. Hence, the IPM package can be piloted and scaled out as an effective alternative to chemical pesticides to manage the insect pests on pak-choi in Cambodia.