In this work, 144 new experimental density values are reported for diethylene glycol monomethyl ether (DEGME) and diethylene glycol monoethyl ether (DEGEE) in the compressed liquid phase between 283.15 K and 353.15 K for pressures up to 25 MPa. The density measurements were performed with an Anton Paar DMA 60/512P vibrating tube densimeter and then correlated by using a Tammann-Tait equation with standard deviations of 1 x 10(-4) g(.)cm(-3). The isothermal compressibility, the isobaric thermal expansivity, and the internal pressure have been determined from the density data. The isothermal compressibility and isobaric thermal expansivity values increase with the size of the diethylene glycol monoalkyl ether molecule. The internal pressure values are lower for DEGEE than for DEGME.