A cordless curtain assembly includes a fabric connected to a top rail. The fabric has multiple transverse folding sections and each folding section has a passage defined therein. Multiple magnetic units are respectively received in the passages of the folding sections and each have a carrier, multiple clamping members and multiple magnetic parts. The carrier of each magnetic unit has two reception areas defined in the top thereof. Each clamping member has a press bar and two legs which respectively extend from the underside of the press bar. Each leg has a resilient arm extending outward therefrom. Each clamping member has one of the magnetic parts clamped between the two legs. The combination of the clamping member and the magnetic part are securely inserted into the reception area corresponding thereto. The press bar seals the top opening of the reception area.