The aim of this study was to evaluate the effect of different capsule filling manufacturing techniques and storage conditions on the release of the active ingredients from herbal capsules during the dissolution test in vitro. Different techniques for the preparation of the original mixture of dry extracts were applied, and subsequently capsules with six different fillings were prepared. The stability of the capsules was evaluated in different long-term storage conditions, registering changes in the water content (loss of drying), capsule disintegration time, and phenolic compounds dissolution test in vitro. The baseline of phenolic compounds release in the control capsules (filled with the mixture of the powder of dry herbal extracts) was the highest, compared to other capsule groups, yet during long-term storage, these capsules accumulated too much moisture, which impeded capsule disintegration time and phenolic compounds release. The study showed that moisture and temperature changes occurring during the storage of the preparation had a negative effect on the release of phenolic compounds from herbal capsules. Capsules filled with pellets demonstrated a uniform and stable release of the active ingredients in different long-term storage conditions, which indicates that the manufacturing technology of dry herbal extracts affects the stability of the active ingredients.