Nowadays, the increasing demand for concrete is causing serious environmental impact including pollution and waste generation, rapid depletion of natural resources, and increased CO2 emission. Incorporating natural fibers in concrete can contribute toward environmental sustainability. This paper is concerned with the use of natural fibers obtained from the plant species Phragmites australis (PA). The plant is invasive, and rapidly grows abundantly along rivers and waterways, causing major ecological problems. This research is part of a wide range investigation on the use of natural fibers produced from the stem of PA plants in concrete. Using a machine, plant stems were crushed into fibers measuring 40 mm in length and 2 mm in width, and treated with 4% NaOH solution for 24 h. A total of four concrete mixes were prepared with varying additions of treated fibers, ranging from 0% to 1.5% (by volume) with water to cement ratio of 0.5% (by volume). Concrete specimens were tested at 3, 7, and 28 days. Testing included compressive strength, density, total water absorption, and capillary water absorption. The results show that incorporating PA natural fibers reduces the water absorption by total immersion and capillary action by up to 45%. Moreover, there is a negligible decrease in concrete density and strength when fibers were added. It is concluded that adding up to 1.5% natural PA fibers to concrete is a feasible strategy to produce an eco-friendly material which can be used in the production of sustainable building material with adequate mechanical and durability performance.