<p>Strength properties of paper with lignin-containing microfibrillated cellulose (LMFC) were investigated under industrial conditions. To achieve this, a conical refiner was used to fibrillate unbleached eucalyptus kraft pulp fibers with low lignin content (LYP) and with high lignin content (HYP). Additionally, industrial white-water samples collected at the beginning and at the end of a paper production run were used in refining and handsheet preparation processes. Comparing the two types of pulp, HYP exhibited superior internal bond strength properties than LYP, attributed to the increased relative bonded area due to the presence of lignin. The introduction of LMFC (at 5 and 10% w/w) derived from both LYP and HYP resulted in significant enhancements in the tensile index, with increases of 34% and 52%, and 26% and 39%, respectively, when tested in demineralized water. Furthermore, it was observed that the white-water with a high cationic demand diminished paper strength, while the white-water with lower fine content enhanced these properties. Notably, the type of water used had a more significant impact on strength properties than the presence of microfibrillated cellulose, although the addition of microfibrillated cellulose improved tensile strength consistently. Alongside strength characteristics, the influence on other paper properties such as structure, oil and water barrier, and optical properties were also examined.</p>