  In this Letter, we investigate the effects of dark energy on $P-V$
criticality of charged AdS black holes by considering the case of the RN-AdS
black holes surrounded by quintessence. By treating the cosmological constant
as thermodynamic pressure, we study its thermodynamics in the extended phase
space. It is shown that quintessence dark energy does not affect the existence
of small/large black hole phase transition. For the case $\omega_q=-2/3$ we
derive analytic expressions of critical physical quantities, while for cases
$\omega_q\neq-2/3$ we appeal to numerical method for help. It is shown that
quintessence dark energy affects the critical physical quantities near the
critical point. Critical exponents are also calculated. They are exactly the
same as those obtained before for arbitrary other AdS black holes, which
implies that quintessence dark energy does not change the critical exponents.
