Introduction: Patients undergoing ileostomy surgery often experience electrolyte disturbances and dehydration, especially during the first post-operative period. Recently, research has also begun on how the newly constructed ileostomy affects the patient’s nutritional status. Aim: The aim of the present pilot study was to assess the nutritional status of patients before and after the construction of the ileostomy as well as nutrition-related factors. Material and Method: This was a pilot study. The sample consisted of 13 adult patients diagnosed with colorectal or colon cancer who underwent scheduled ileostomy surgery. The evaluation tool used was “Original Full Mini Nutritional Assessment (MNA)”. Patients underwent nutritional assessment before the surgery (time 0), on the 7th post-operative day (time 1), and on the 20th post-operative day (time 2). The statistical significance level was set at p < 0.05. Results: All patients had a drop in MNA score on the 7th and 20th post-operative days. Factors associated with MNA were weight loss, mobility, body mass index (BMI), number of full meals consumed per day, portions of fruits and vegetables consumed per day, and mid-arm circumference, p < 0.05, respectively. Pre-operatively, 38.5%, of patients had severe weight loss (>3 kg), 23% moderate weight loss and 38.5% minimal weight loss. Pre-operatively, 92.3% of participants were able to move on their own and 69.2% on the 20th post-operatively day. Furthermore, BMI >23 kg/m2 had 84.6% of participants pre-operatively and 30.8% on the 20th post-operative day. In terms of portions of fruits and vegetables consumed per day, 30.8% of patients consumed at least 2 times, pre-operatively and no one (0%) on the 20th post-operative day. Moreover, pre-operatively all participants (100%) had arm circumference >22 cm while on the 20th post-operative day, only 38.5% of participants had arm circumference >22 cm. Conclusions: In the first 20 days after the construction of an ileostomy, the nutritional status of the patients is significantly affected. Decreased patient nutrition in both quantity and ingredients and reduced fluid intake appear to adversely affect the patient’s nutritional status.