Background: Sublingual immunotherapy (SLIT) has shown promise in mitigating allergic asthma symptoms; nevertheless, its high dose and prolonged duration of treatment raise safety concerns. This study explored the potential of Lactobacillus paracasei (L. paracasei) to enhance the effectiveness of SLIT in a mouse model of allergic asthma. Methods: Allergic asthma was induced in Balb/c mice following sensitization and challenge with a house dust mite (HDM) allergen. Subsequently, the mice were subjected to SLIT (66 and 132 µg) either alone or in combination with L. paracasei supplementation. Asthma-associated parameters, including rubbing frequency, IgE level, cytokine profiles, and histological changes, were evaluated to assess treatment efficacy. Results: mice that received SLIT 132 µg combined with the probiotic (combined 132) demonstrated a significant reduction in allergic symptoms (rubbing). This treatment strategy led to a marked IgE and eosinophil level decrease in serum; an increase in anti-inflammatory cytokines like IFN-γ and IL-10; and a reduction in pro-inflammatory cytokines IL-17 and TNF-α. The combination therapy also mitigated lung inflammation and supported the restoration of the structural integrity of the colon, promoting the recovery of goblet cells and mucus secretion. Probiotic treatment alone also effectively reduced IgE levels, increased IFN-γ, and decreased levels of IL-17 and TNF-α. Conclusions: The adjuvant effect of L. paracasei in enhancing SLIT represents a promising approach for improving asthma treatment efficacy.