Thermal chaos under spatially/temporally periodic perturbations in the extended phase space of Bardeen-AdS black holes surrounded by quintessence dark energy is investigated. The occurring condition of chaos is obtained with the Melnikov integral. It is shown that the spatial chaos is always supposed to occur even for a tiny spatially periodic perturbation imposed on the equilibrium configuration. However, the temporal chaos will arise in the unstable spinodal region only if the given perturbed amplitude γ is larger than a critical value γ c . The value of γ c is determined by the magnetic monopole charge β, the initial temperature T 0 , the quintessence state parameter ω, and the quintessence normalization parameter a. Particularly, combining the effects of ω and a together, we find that the quintessence appears quite similar to an enhancing/damped mechanism. In other words, there exists a critical value ρ c of the quintessence dark energy density ρ. In the region of ρ < ρ c , the existence of quintessence leads to a reduction in the viscosity of black holes and thus makes the system more likely to exhibit chaotic behavior. Conversely, given the energy density ρ > ρ c , the system acquires higher viscosity so that it is endowed with the ability of enduring a larger thermal fluctuation.