Contribution: Gender mainstreaming in university teaching should be covered in all the knowledge areas. This work successfully introduces the gender perspective as part of the methodological approach to teaching and learning in Computer Science. Background: This study describes how gender mainstreaming has been introduced and matured during six academic years, from 2016-2017 to 2021-2022, in Software Engineering I course in the Degree of Computer Science at the University of Salamanca. Intended Outcomes: The aim that has been pursued is to raise awareness among students of Computer Science about equality, equity, inclusion, and respect for diversity to build better professional ethics and advance in eliminating any gender-related gap in Computer Science. Application Design: The introduction of gender mainstreaming in the Software Engineering I course has been done in six stages to advance in the gender-gap reduction improving in each academic year with the experience and voluntary feedback from the students of the previous year, using anonymized questionnaires. Findings: Gender mainstreaming requires special attention in careers with a visible gender gap, such as Computer Science. Incorporating the gender perspective as part of the teaching-learning process does not have a measurable impact in a short period but instead aims to make software engineers reflect in such a way that they reason about the need to promote diversity in software development contexts.