Introduction: Diarrhea is a condition in which faeces are discharged from the bowels frequently and in a liquid form. Dehydration is a very common phenomenon of diarrhea. Severe dehydration may cause electrolyte and acid-base imbalance in human body. So electrolyte and acid-base status analysis is a vital part of treating children with acute diarrhea. Aim of the study: The aim of this study was to evaluate the electrolyte and acid-base status in children with dehydration caused by acute diarrhea. Methods: This was a prospective observational study and was conducted in the Department of Paediatric Medicine of Dr. M R Khan Shishu Hospital & ICH, Dhaka, Bangladesh during the period from January 2017 to June 2017. In total 81 children aged under 5 years admitted to the mentioned hospital with dehydration caused by acute diarrhea were selected as the study population. Result: In our study we found 53.09% (n=43) patients had is onatremic dehydration (Na+: 135-145 mEq/L) followed by 23 (28.40%) patients who had hyponatremic dehydration (Na+<135 mEq/L). Among those 28.40% patients 6.17% (n=5) had Na+<120 mEq/L. On the other hand, 15(18.51%) children had hypernatremic dehydration (Na+>145mEq/L). Among those 18.51% children 1.23% (n=1) patients had Na+<160 mEq/L. Besides these, among total study population hypokalemia (serum K+<3.5 mEq/l) were in 67.90% (n=55) patients and hyperkalemia (serum K+>4.5mEq/l) were in 6.17% (n=5) patients. So 25.93% (n=21) patients had normal serum potassium level. Conclusion: Hypokalemia is the most common electrolyte abnormality in acute diarrhoea with dehydration followed by hyponatremia and hypernatremia. Significant number of patients also developed metabolic acidosis.