<p>Edible insects, such as mealworms (<i>Tenebrio molitor</i>), have gained attention as sustainable protein sources due to their minimal resource requirements for cultivation and high nutritional value. This study evaluated the effects of dietary supplementation with probiotics (<i>Lacticaseibacillus</i>, <i>Lactobacillus</i>, and <i>Bifidobacterium</i>) and their cell-free supernatants (CFSs) on the growth and microbial safety of mealworms. Results showed that both probiotics and CFSs significantly enhanced growth performance and survival rates (<i>p</i> &lt; 0.05). Notably, <i>Bifidobacterium bifidum</i> BGN4 yielded the highest weight gain (192.1&#xa0;mg), length gain (20.0&#xa0;mm), and specific growth rate (9.2%), while reducing mortality to 3.3%. Dietary supplementation also increased lactic acid bacteria populations and inhibited indicator microorganisms, including aerobic bacteria, coliforms, and yeasts and molds. Furthermore, four <i>Bifidobacterium</i> CFSs eliminated <i>Listeria monocytogenes</i> within 7&#xa0;days. These findings highlight the probiotics and their CFSs effectively improve mealworm growth performance and microbial safety, providing an improved approach to edible insect production.</p>