<p>Electrochromic (EC) materials are of great interest for applications in smart windows, displays, and energy-efficient devices. Among them, triarylamine-based polymers stand out due to their colorless neutral state, tunable colors, rapid switching speed, and favorable processability. Most triarylamine-based polymers exhibit green and blue electrochromism upon oxidation. In our efforts to develop attractive EC materials, we focus on magenta EC polymers incorporating <i>N</i>-phenylphenothiazine units. A straightforward synthetic strategy was employed to create a novel <i>N</i>-phenylphenothiazine-based diamine, which was subsequently used in polycondensation reactions with commercially available aromatic dicarboxylic acids and dianhydrides to develop two series of innovative polyamides and polyimides. The polymers demonstrated excellent solubility in various organic solvents and could be solution-cast into robust, well-adhered films on indium tin oxide (ITO)-glass substrates. They also exhibited favorable thermal stability, with no significant weight loss observed before 350&#xa0;°C and moderately high glass transition temperatures (<i>T</i>_g) ranging from 238 to 316&#xa0;°C. Upon electrochemical oxidation, the polymers displayed well-defined and reversible redox couples, with half-wave oxidation potentials (<i>E</i>_1/2) ranging from 0.60 to 0.77&#xa0;V. In the oxidized state, the polymers exhibited an absorption band around 550&#xa0;nm along with a distinctive magenta coloration. The incorporation of <i>tert</i>-butyl substituents on the phenothiazine active sites reduced the oxidation potential and enhanced both redox and electrochromic stability.</p>