Our study site locates in a mine site in Hokkaido, Japan. The wastewater from the mine contained high concentration of harmful metals, which are removed as sediment and stored in a tailing dam. High concentration of harmful metals could inhibit plant growth. However, Abies sachalinensis were found to grow in the tailing dam. This study was conducted to elucidate mechanisms of harmful metal tolerance in A. sachalinensis. Abies sachalinensis accumulated high concentrations of Al in roots. To detoxify Al, A. sachalinensis should produce detoxicants. Analysis of detoxicants in roots revealed that A. sachalinensis produced condensed tannin, suggesting that condensed tannin could reduce Al toxicity. As other harmful metal tolerance in plants, endophytic fungi living in plant roots are known to enhance harmful metal tolerance in plants. Therefore, roots of A. sachalinensis were surface-sterilized, and endophytic fungi were isolated. The isolated root endophytes were used for assay of production activity of Al detoxicants. The assay revealed that the species with the highest appearance rate showed the highest production activity of Al detoxicants. These results suggest that A. sachalinensis could acquire Al tolerance mechanisms via producing condensed tannin and infection by endophytic fungi with high production activity of Al detoxicants.