This study aimed to screen lactic acid bacteria (LAB) strains isolated from various traditional Chinese pickles for the ability to produce γ-aminobutyric acid (GABA) and to evaluate their in vitro probiotic properties. Among 117 isolates, strain XD117 showed the highest GABA-producing capacity, producing (1.693 ± 0.042) mg/mL of GABA when cultured in an artificial medium. The strain was identified as Lactiplantibacillus plantarum by morphological observation and 16S rRNA gene sequencing, and it showed high survival rates after exposure to acidic conditions, high bile salt concentrations or simulated gastrointestinal environments. An enzymatic hydrolysate of dried stems of Dendrobium officinale was fermented with L. plantarum XD117. The GABA concentration of the fermentation broth was up to 2.88 mg/mL, with a viable count of 10⁹ CFU/mL. In vitro cell experiments showed that the fermentation broth significantly reduced the levels of the inflammatory cytokines interleukin 1β (IL-1β), tumor necrosis factor-α (TNF-α), and interleukin 6 (IL-6) in RAW264.7 cells induced by lipopolysaccharides (LPS) (P < 0.05); moreover, the higher the GABA content, the more pronounced the inhibitory effect on IL-6 and IL-1β. This study provides a theoretical basis for the application of the probiotic strain L. plantarum XD117 in the field of functional fermented foods and offers a new approach for the high-value development of D. officinale.