Caligus minimus, known as a sea louse, is a very important pathogen of sea floating cage culture. This paper describes the life cycle of Caligus minimus isolated from seabass culture in the cage in Penang, Malaysia. The parasitic copepod development was observed at 30 °C and 20 °C, with ambient photoperiod under laboratory conditions. Female of Caligus minimus with matured eggs were collected and incubated in a beaker with slow aeration. The life cycle consists of nine stages: two nauplii, one copepodid, four chalimi, pre-adult, and adult. The copepodid is infective, and all subsequent stages were attached to fish and did not require an intermediate host for its development. The eggs hatched out within 48 h at 30 °C and within 60 h at 20 °C, and two nauplii stages were recorded after 1.88 ± 0.74 h and 4.23 ± 1.02 h, respectively. Copepodid stage was informed after 24.91 ±
2.24 h. A single experiment conducted by exposing an uninfected sea bass fingerling to copepod showed the copepodid immediately attached to the body, fins, and gills of the fish. Chalimus stage was observed after 20.95 ± 3.70 h followed by pre-adult stage after 45.88 ± 5.95 h.Within 44.5 ± 1.08 h, the adult was found and showed the female became mature and lay the eggs after 43.25 ± 3.11 h. At 20 °C, Copepodid was recorded after 25.86 ± 1.40 h and completed Chalimus stage within 40 h. Conclusively, 5.5–10 days were needed for Caligus minimus to complete its life cycle at tested temperature.