  In this paper, we study generalized Douglas-Weyl $(\alpha, \beta)$-metrics.
Suppose that an regular $(\alpha, \beta)$-metric $F$ is not of Randers type. We
prove that $F$ is a generalized Douglas-Weyl metric with vanishing S-curvature
if and only if it is a Berwald metric. Moreover by ignoring the regularity, if
$F$ is not a Berwald metric then we find a family of almost regular Finsler
metrics which is not Douglas nor Weyl. As its application, we show that
generalized Douglas-Weyl square metric or Matsumoto metric with isotropic mean
Berwald curvature are Berwald metrics.
