Background: Hypertension is a common early adverse event of anti-angiogenic treatment of cancer and may associate with treatment response. However, blood pressure measurement as a surrogate response biomarker has methodological limitations, and predictive biomarkers of angiogenesis inhibitors are lacking. In disease associated with hypertension, vasoactive peptides have been linked to cardiovascular pressure load. Here, we have explored potential associations between circulating levels of vasoactive peptides and tumor response during bevacizumab-containing treatment of colorectal cancer. Material and methods: Metastatic colorectal cancer (mCRC) patients with available best objective response (ORR) and time to tumor progression (TTP) data were included from a randomized clinical trial investigating maintenance therapy after first line chemotherapy plus bevacizumab. Midregional-pro-adrenomedullin (MR-proADM), midregional-pro-atrial-natriuretic-peptide (MR-proANP), and C-terminal-prepro-vasopressin (Copeptin) vasoactive peptide concentrations were measured in plasma at baseline and after 6 weeks of chemotherapy and bevacizumab treatment ( n = 97). We determined associations among clinical outcome (ORR and TTP), peptide levels, and hypertension (NCI-CTCAE 4.0 criteria), using Spearman’s test, multiple linear regression, and Mann–Whitney’s test. Results: Increasing levels of vasoactive peptides from baseline and after six weeks of treatment were associated with improved treatment outcome (MR-proADM: ORR, p = .0003; TTP, p = .05; MR-proANP: ORR, p = .05; TTP, p = .03; Copeptin: ORR, p = .10; TTP, p = .02). Patients with increasing levels of all three peptides (n = 28) versus increasing levels of one or two peptides ( n = 59) showed a median TTP of 284 and 225 d, respectively ( p = .02). Conclusions: Our results suggest that increasing systemic levels of vasoactive peptides associate with improved tumor response and TTP in mCRC patients treated with a bevacizumab-containing regimen. These findings support the proposed link between the tumor vasculature and the cardiovascular system of the host. This should motivate further studies that investigate the potential role of vasoactive peptides as a novel class of dynamic biomarkers in the treatment of cancer.