Background Globally, 1,096,601, 704,376, and 48,541 new colon, rectum, and anus cancer cases were recorded in 2018, respectively. Besides, 551,269, 310,394 and 19,129 cases of colon, rectum, and anus cancer deaths occurred in the same year. As a result, these cancers ranked in the third level of cancer incidence, and in the second level of cancer mortality. As it is known, all cancer patients are subjected to cancer-induced and therapy-induced nutritional deficiencies (mainly of proteins and calories). The present study aimed to assess proteins level in colorectal cancer (CRC) patients who underwent surgery and chemotherapy. Methods A combined retrospective and prospective study was performed. The present study enrolled 100 CRC patients with their data on surgical procedures and chemotherapy management. Assessments of the studied samples were conducted as a baseline before receiving chemotherapy and preoperatively as P0, while the period after that was termed as P1. The serum samples were collected to measure protein concentration. Total Protein Kit, Micro was used. Results The mean age of the patients was 50.7 ± 12.88 years old. Only 8% had a positive CRC family history. Rectosigmoid cancer represented the most frequent site, figured in 41% of the cases, followed by rectum cancer. Multiple sites of CRC metastasis were recorded in 15% of the patients. All patients received chemoradiation. Folinic acid (leucovorin), 5-FU, and oxaliplatin (FOLFOX) was the most used regimen, administered in 40% of the patients. Oxaliplatin and capecitabine (also called Xeloda) (XELOX) were administered in 14% of the patients. Folinic acid (leucovorin), 5-FU, oxaliplatin, and irinotecan (FOLFOXIRI) were administered in 16% of the patients. Single-agent oxaliplatin or carboplatin were administered in 6% of the patients, each. 5-FU plus leucovorin was administered to12% of the patients. Three patients received irinotecan, and oxaliplatin (IROX). One patient received folinic acid (leucovorin), 5-FU and irinotecan (FOLFIRI). Also, Gemzar was administered to two patients only. A total of 80% of the patients underwent several surgical procedures. Anterior perineal resection (APR) and total mesorectal excision (TME) were the most common two surgeries, performed in 20 and in 30% of the patients, respectively. In P0 status, 44% of the patients suffered from low protein levels, and 13% of the patients were within the normal level. These findings were statistically different (p = 0.03). After CRC management (i.e., P1 status), 70% of the patients had protein deficiency. These results have strong significant differences (p = 0.000). The mean of protein concentration declined gradually after management, from 8.82 ± 0.9 μg/L to 6.21 ± 0.78 μg/L, with a strong association between a reduction in proteins levels towards deficiency and surgical procedures and chemotherapy protocols (p = 0.000). Conclusion The incidence of CRC is increasing annually, and the chance of being diagnosed with this type of cancer has risen in recent years. In the present study, the male to female ratio was 1:1.5, and the 5th decade of life was the most common age for the diagnosis of CRC. A negative family history and bowel inflammatory diseases (IBD) history did not exclude people from exposure to the incidence of CRC. Colorectal cancer with localized and moderately differentiated adenocarcinoma were the most common types in the present work. Tumor distance from the anal verge seems to be very important and plays a significant role in the choosing of surgical intervention types and chemoradiation protocols. Colorectal cancer acts as a complex condition and, in addition to its management, nutritional state influences it in different mechanisms. Most patients suffered from hypoproteinemia after surgery and chemoradiation. As a result, alteration in the treatment outcomes, delaying in wound healing, and an increase in postoperative complications may occur.