Landfills are significant sources of methane, which contributes to climate change. As an alternative to mitigation by gas utilization systems, bio-mitigation systems may be implemented. Such systems are based on microbial methane oxidation in full surface biological covers, so-called biocovers, or open or closed bed biofilter systems. The objective of this paper is to describe the relationship between research on process understanding of the oxidation of landfill gas contained methane and the up-scale to full bio-mitigation systems implemented at landfills. The oxidation of methane is controlled by several environmental factors such as soil texture, temperature, soil moisture content, methane and oxygen supply, and nutrients, and both soils and compost materials have been shown to exhibit high methane oxidation rates. For compost materials high methane oxidation is observed even during cold periods due to self-heating processes. Bio-mitigation can be used as a stand-alone technology or combined with active or passive gas collection. When implementing bio-mitigation systems focus should be on additional fugitive methane emissions or the presence of uncontrolled point releases. A protocol for implementing a bio-mitigation system is presented, and the reported landfill-implemented bio-mitigation systems either established as full-scale or pilot-scale systems are reviewed. It is concluded that bio-mitigation systems have a large potential for providing cost-efficient mitigation options for reducing methane emissions when landfill gas utilization systems cannot be implemented or cease to perform as cost-efficient, sustainable solutions.