Methane (CH4) is emitted from landfills around the world and accounts for approximately 18% of global anthropogenic CH4 emissions. Despite the existing conventional gas collection systems, a considerable amount of landfill gas that is generated is released to that atmosphere as fugitive gas. Engineered landfill biosystems have been utilized to capture this gas that escapes from landfills with the aid of biological CH4 oxidation performed by methanotrophic bacteria. By providing optimum growth conditions, methanotrophic bacteria have been cultivated in a number of engineered biosystems such as biocovers, passively or actively vented biofilters, bio-windows and interim bio-tarps, to mitigate the CH4 emissions in landfills. According to previous studies, the incorporation of plants in landfill biosystems can have both positive and negative impacts on the microbial aerobic CH4 oxidation process. In a column experiment conducted, a significantly lower CH4 oxidation rate was observed in the vegetated flow-through columns, and it was hypothesized that this observation was made due to the preferential pathways created by the plant root systems for CH4 to escape. The bare soil column exhibited the highest CH4 oxidation rate of 455 gCH4/m2/day, while the maximum CH4 oxidation rates for the vegetated columns ranged between 147 to 171 gCH4/m2/day. In the methanotrophic quantification study done, it was observed that population levels were much greater in bare soil columns when compared to vegetated columns. In the lysimeter experiment, the lowest CH4 oxidation rates were observed in the lysimeter with alfalfa plants but there were no statistically significant differences in oxidation rates between the bare soil and native grass covered lysimeters. In addition, Methylobacter was the dominated genus in the lysimeters constructed with the compost mixture while Methylocystis dominated in the lysimeters constructed with topsoil. Investigating the influence of plants on soil-gas diffusivity showed that DP values ranged between 6.50 × 10-6 to 1.02 × 10-6 m2s-1 in the vegetated through-flow column and 2.8 × 10-6 to 2.53 × 10-7 m2s-1 in the bare soil through-flow column. This research showed that the presence of vegetation had a profound effect on the performance of biological CH4 oxidation in engineered landfill biosystems.