This paper presents a research to determine the effects of the Northeast Monsoon (NEM) and the Southwest Monsoon (SWM) on wave power along the coastal area of Mandi Darah Island, Sabah. This study identified the daily data of wave height and wave period for 6 months from June to December 2018. The following period was chosen because it consisted of two monsoon seasons in Sabah. The data obtained from the Acoustic Doppler Current Profiler (ADCP) were thoroughly analyzed to estimate the wave height and the wave period to identify the wave power at Mandi Darah Island. The wave heights ranged from 0.01 m to 0.47 m while the wave periods ranged from 1.0 s to 8.6 s. The wave height range during the NEM was higher by 0.12 m than SWM, while the difference of wave period was significantly higher by 2.17 s during the NEM. The maximum wave power recorded at Mandi Darah Island was 1.57 kW/m throughout the period. During NEM, the wave power was significantly higher than during SWM, by 0.70 kW/m. These findings led to determining the wave energy type converter that suits the wave conditions at the Mandi Darah Island coastal area.