High altitude young tea leaves are the most preferred raw material for high quality tea production while old tea leaves were considered low quality. This study examined the chemical compounds in tea leaves such as (+)-catechin (C), (-)-epicatechin (EC), (-)- epigallocatechin (EGC), (-)-epicatechin gallate (ECG), (-)-epigallocatechin gallate (EGCG), caffeine, gamma aminobutyric acid (GABA) and total phenolics content (TPC) in different maturity stages of tea leaves from highland (HP01, HP02 and HP03) and lowland (LP) tea plantation in Malaysia. The results showed that young tea leaves from samples HP01, HP02 and LP contain high GABA, caffeine and TPC as compared to old tea leaves. However, with the exception of caffeine, old tea leaves from sample HP03 contained higher TPC and GABA than young tea leaves. In addition, the highest accumulation of GABA was found in a bud from HP01. However, in general, the accumulation of GABA was high in LP (lowland) tea leaves from bud until 4th leaves when compared to highlands tea leaves. Furthermore, the number of catechins with a high concentration in a very young leaf was HP01>LP01>HP02>HP03. The major catechins were identified as EGC (49.02 mg/g) and the minor was ECG (1.17 mg/g). Overall, the accumulation of catechins, caffeine and phenolics content was high in tea leaves at high altitudes whereas GABA content was high in tea leaves at low altitudes. This finding provides information on bioactive metabolites distribution in different maturity stages of tea leaves from high- and lowland tea plantations in Malaysia.