A method for decoding an error correction code and an associated decoding circuit are provided, where the method includes the steps of: calculating a set of error syndromes of the error correction code, where the error correction code is a t-error correcting code and has capability of correcting t errors, and a number s of the set of error syndromes is smaller than t; sequentially determining a set of coefficients within a plurality of coefficients of an error locator polynomial of the error correction code according to at least one portion of error syndromes within the set of error syndromes for building a roughly-estimated error locator polynomial; performing a Chien search to determine a plurality of roots of the roughly-estimated error locator polynomial; and performing at least one check operation to selectively utilize a correction result of the error correction code as a decoding result of the error correction code.