The new version of the Brazilian Forest Code prescribes a 30 m forest buffer around small width streams (less than 10 m width) as Areas of Permanent Preservation (APPs), to ensure water supply, erosion control, and biodiversity conservation. We tested the effectiveness of the prescribed buffer in maintaining lizard assemblages in riparian forests associated with small width streams in the Cerrado of central Brazil. We used a capture-recapture study in three riparian forests: two in protected areas, and one deforested until the limit imposed by law. We captured lizards using pitfall traps with drift fences during a period of 12-14 months in each forest. We recorded 11 lizard species during the sampling period. The reduced riparian forest had lower abundance, richness, evenness, and phylogenetic diversity compared to the preserved habitats. This forest also lacked forest specialist species (e.g., Enyalius bilineatus), bearing an assemblage composed exclusively by two generalist and synanthropic species (Tropidurus torquatus and Ameiva ameiva). Our results indicate that the new Brazilian Forest Code is inadequate to ensure the protection of lizard assemblages in Cerrado riparian forests, and should take into account larger riparian buffers associated with small rivers, and also consider other factors such as the environmental quality around areas of permanent protection along riparian forests.