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Colistin is a last-resort antimicrobial for treating multidrug-resistant Gram-negative bacteria. Phenotypic colistin resistance is highly associated with plasmid-mediated mobile colistin resistance (<i>mcr</i>) genes. <i>mcr</i>-bearing <i>Enterobacteriaceae</i> have been detected in many countries, with the emergence of colistin-resistant pathogens a global concern. This study assessed the distribution of <i>mcr-1</i>, <i>mcr-2</i>, <i>mcr-3</i>, <i>mcr-4</i>, and <i>mcr-5</i> genes with phenotypic colistin resistance in isolates from diarrheal infants and children in Bangladesh. Bacteria were identified using the API-20E biochemical panel and 16s rDNA gene sequencing. Polymerase chain reactions detected <i>mcr</i> gene variants in the isolates. Their susceptibilities to colistin were determined by agar dilution and E-test by minimal inhibitory concentration (MIC) measurements. Over 31.6% (71/225) of isolates showed colistin resistance according to agar dilution assessment (MIC > 2 μg/mL). Overall, 15.5% of isolates carried <i>mcr</i> genes (7, <i>mcr-1</i>; 17, <i>mcr-2</i>; 13, and <i>mcr-3</i>, with co-occurrence occurring in two isolates). Clinical breakout MIC values (≥4 μg/mL) were associated with 91.3% of <i>mcr</i>-positive isolates. The <i>mcr</i>-positive pathogens included twenty <i>Escherichia</i> spp., five <i>Shigella flexneri</i>, five <i>Citrobacter</i> spp., two <i>Klebsiella pneumoniae</i>, and three <i>Pseudomonas parafulva</i>. The <i>mcr</i>-genes appeared to be significantly associated with phenotypic colistin resistance phenomena (<i>p</i> = 0.000), with 100% colistin-resistant isolates showing MDR phenomena. The age and sex of patients showed no significant association with detected <i>mcr</i> variants. Overall, <i>mcr</i>-associated colistin-resistant bacteria have emerged in Bangladesh, which warrants further research to determine their spread and instigate activities to reduce resistance.