Acetylbutyrolactone was applied as a fluorogenic reagent for developing a simple, selective and economic method for determination of Two Gamma-Aminobutyric Acid (GABA) analogues containing primary aliphatic amine group (gabapentin and pregabalin). The reaction depends on the formation of Schiff bases which have strong fluorescence activities at 440 nm after excitation at 380 nm. The different reaction parameters that affect the stability of the formed Schiff base have been deeply investigated and optimized. The suggested reaction mechanism has been explained. The fluorescence-concentration plots were rectilinear over the range of 20-100 µg ml-1 for gabapentin and 10-100 µg ml-1 for pregabalin with excellent correlation coefficients (0.9998 for Gabapentin and 0.9999 for pregabalin). The lower quantification limits were 2.9 and 1.9 µg ml−1 for gabapentin and pregabalin, respectively. According to ICH guidelines, the method was validated and the results were in agreement with other reported methods in respect to accuracy and precision. Determination of gabapentin and pregabalin in the commercial capsules were achieved using the proposed method with excellent recoveries (100.22% for Gaptin® capsules and 100.28% for Lyrolin® capsules) and high degree of accuracy.