This longitudinal study investigated the academic and cognitive characteristics of persistent mathematics difficulty (MD-p) from first to fourth grade. Ninety-nine children were retrospectively categorized into one of three groups: MD-p, transient mathematics difficulty (MD-t), or typically developing. MD-p was defined as persistently low mathematics achievement (≤25th percentile) in at least 2 years from first to fourth grade. The results indicated that the MD-p group was more likely than other groups to have deficits in calculation, practical problem solving, number facts, and reading. In terms of cognitive characteristics, MD-p was specifically characterized by deficits in math concepts and phonological decoding, though there was some evidence for the involvement of working memory, processing speed, and numerical reasoning.