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The double-spined bark beetle, <i>Ips duplicatus</i>, is an example of a species whose economic importance has increased in many European countries over the past decade. Many aspects of its life cycle remain unknown, complicating its management. <i>I. duplicatus</i> adults overwinter in forest litter, which makes the removal of infested trees during winter ineffective. Therefore, this study focuses on the mechanisms and timing of <i>I. duplicatus</i> overwintering migration into the forest litter. Only 2.2% of adult <i>I. duplicatus</i> overwintered under the bark of spruce logs stored outdoors from August 2016 to March 2017. In all, 94.4% of the beetles emerged and burrowed in forest litter. Migration began in late August, peaked in mid-September, and lasted until mid-October. At that time, forest litter collected at the base of an infested tree contained an average of 154.7 ± 23.9 <i>I. duplicatus</i>. Catches of migrating adults on glue stripes proved that the beetles walked down the trunk on days when the average daily temperature reached 10–15 °C. Based on the results, we suggest that trees infested with <i>I. duplicatus</i> that have completed their development into adults should be removed no later than September. Sanitation cutting in the following months is not effective against this pest.