Oil palm (Elaeis guineensis) is considered as the world's leading edible oil producing plant and in tropical countries well established as a perennial plantation crop. Oil palm has spread over 10,000 hectares in the wet zone of the Island. Immature phase of oil palm plantation up to 5 years, there is sufficient space available inside the cultivation. Land productivity in immature plantations could be sustainably increased with some selected intercrops. A field experiment is being conducted at Thalgaswella Estate (6° 24′ 60″ °N, 80° 27′ 44″ °E. 48 m above sea level, WL2a) in Galle district to investigate the suitability of different intercrops during the immature phase. Banana, ginger, and turmeric were selected as intercrops. The experiment was designed with Randomized Complete Block Design (RCBD) with four treatments, including three replicates. Growth parameters of intercrops and maincrop were taken at 2 months intervals. Yield of intercrops were taken accordingly. In addition to this, the chlorophyll content of leaves was also measured in both intercrops and main crop. Soil chemical parameters were measured annually. There was a significant difference in the height of banana plants and the leaf width of Turmeric grown under oil palm during the first year of this experiment. Intercropped turmeric, ginger, and banana have given yields 4875, 4500, and 7550 kg/ha, respectively. During immature phase of the oil palm hardly any income to the grower, hence intercropping will give a very good chance to gain an income before the first harvest of oil palm being done. Percentage yields of intercrops were shown in banana, turmeric, and ginger as 60.64%, 32.8%, and 61.22% respectively against the monocrop and findings will help to make sustainable use of lands in oil palm plantations.