Bacterial cellulose (BC)/κ-carrageenan composite pellicles were prepared by in situ formation and subjected to post-formation alkali and neutralization treatments. κ-Carrageenan was incorporated into BC pellicles by in situ formation to form a gel by post-formation treatment with a solution containing K+. Structural analyses indicated that BC/κ-carrageenan pellicles had a double-stage structure, consisting dominantly of cellulose in the upper part and κ-carrageenan in the under part. BC/κ-carrageenan pellicles became weaker upon application of a tensile force and were harder compared with the BC pellicles. Vanillin was used to study the release of active agents from the pellicles. The fractional release of vanillin from BC/κ-carrageenan pellicles relative to the initial release (30–60 min) was greater than that from BC pellicles. These findings should aid basic research on BC/κ-carrageenan pellicles and help in determining their suitability for application in the biomedical and cosmetic industries.