  We compute the gravitational waves generated by compact binary systems in a
class of massless scalar-tensor (ST) theories to the 1.5 post-Newtonian (1.5PN)
order beyond the standard quadrupole radiation in general relativity (GR).
Using and adapting to ST theories the multipolar-post-Minkowskian and
post-Newtonian formalisms originally defined in GR, we obtain the tail and
non-linear memory terms associated with the dipole radiation in ST theory. The
multipole moments and GW flux of compact binaries are derived for general
orbits including the new 1.5PN contribution, and comparison is made with
previous results in the literature. In the case of quasi-circular orbits, we
present ready-to-use templates for the data analysis of detectors, and for the
first time the scalar GW modes for comparisons with numerical relativity
results.
