This paper introduces octave_mermaid_js, a software package for GNU Octave that enables the generation and visualization of diagrams using Mermaid.js syntax directly within the Octave environment. The package allows users to create, display, and save a wide variety of diagrams—including flowcharts, sequence diagrams, class diagrams, Gantt charts, and more—using simple Octave function calls. By bridging the gap between Octave's computational capabilities and Mermaid.js's powerful diagramming tools, octave_mermaid_js enhances the expressive and documentation capabilities of Octave users, particularly in research, education, and technical reporting.