We present radial velocities of the double-lined spectroscopic binary NP Aqr .
The radial velocities and the optical light curves obtained by Hipparcos and ASAS-3 are analyzed separately .
The masses of the primary and secondary components have been found to be 1.65 \pm 0.09 and 0.99 \pm 0.05 M _ { \odot } , respectively .
The cross-correlation functions indicate triple peaks which show presence of a tertiary star .
The spectroscopic properties of this additional component resemble to that of the primary star .
The analysis of the light curves yielded that the more massive primary star fills its corresponding Roche lobe .
The secondary component is at or near Roche lobe indicating a new \beta Lyrae-type near-contact binary .
The orbital inclination is about 40 ^ { \circ } and , therefore , the observed light variations are produced only by the proximity effects .
Due to the absence of eclipses , the effective temperature of the secondary star and the radii of the components could not be determined accurately .
We conclude that NP Aqr is a non-eclipsing double-lined spectroscopic binary with a distance of about 134 \pm 7 pc .
The absolute parameters of the components are also compared with the evolutionary models .
While the location of the primary star seems to be suitable with respect to its mass in the Hertzsprung-Russell diagram , the secondary component is located as if a star having a mass less than 0.6 M _ { \odot } .
This discrepancy is originated from very low effective temperature determined only from the light curve produced by proximity effects .
The distance to the third star appears to be very close to that of the close binary which indicates that it may be dynamically bounded to the binary .