A chemotherapy induced phlebitis severity (CIPS) scale was developed in patients receiving anthracycline chemotherapy for breast cancer. A five-point severity scoring scale for chemotherapy-induced phlebitis was tested for inter-rater reliability. Ease of use was observed through timing assessments and a review of the completeness of documentation. A comparison of CIPS scale grade with participant reported severity scores was made. The final version was tested for inter-rater reliability, with 122 patient assessments. There was an 89.3% (109 of 122) agreement between the assessors (κ = 0.82, SE ± 0.042, 95% CI 0.74–0.90). Mean time to complete the scale was 1 min 36 s and documentation was fully completed for 98% of assessments. Patient reported severity closely matched the CIPS grade (κ = 0.54, SE ± 0.045, 95% CI 0.46–0.63). This new scale provides a list of symptoms associated with chemotherapy phlebitis, which can be scored quickly and accurately. It provides a reliable method for assessing chemotherapy-induced phlebitis, enabling a better understanding of its impact on patients’ quality of life, and to inform the appropriate choice of peripheral or central intravenous administration. Multicentre testing of the CIPS scale is recommended.