Textile industries are increasingly shifting toward eco-friendly fibers in response to environmental concerns, regulatory pressures, rising raw material costs, and growing consumer demand for sustainable apparel. In this context, a sustainable tri-blend yarn was developed using eco-viscose, recycled cotton, and modal fibers. The eco-viscose comprised a 30/70 blend of Circulose and Ecovero pulps, where Circulose is derived from post-consumer cotton textile waste and Ecovero originates from sustainably managed wood sources. Recycled cotton was incorporated as a partial substitute for virgin cotton, while a substantial proportion of modal fiber was included to enhance the mechanical performance required for fabric production. An extreme vertices mixture design combined with response surface methodology was employed to optimize the blend proportions. The design generated fourteen experimental runs, including replicates. Yarn quality parameters were evaluated, and regression models were developed to describe the responses. The optimization targeted minimization of unevenness, imperfection index, and hairiness, alongside maximization of count strength product (CSP), tenacity, and elongation. The optimal blend composition was obtained as 40.0% eco-viscose, 20.3% recycled cotton, and 39.7% modal. Experimental validation showed good agreement with predicted values, with deviations ranging from 0.23% to 4.97%, confirming the adequacy and reliability of the developed models.

eco-viscose, circulose, ecovero, sustainable yarn, recycled cotton, mixture design