Roger Andermatt, 36, killed his elderly victims - who were residents of care homes in central Switzerland - by using tranquilisers or by smothering them with a plastic bag or a cloth.
Andermatt was also found guilty of attempting to murder five more people. All of his victims were aged between 66 and 95.
He was also ordered to pay 75,000 Swiss francs (€48,500) compensation to dependants of four of his victims and court costs of 191,000 francs (€123,500).
Andermatt - nicknamed the “angel of death” by Swiss media - is the country’s worst serial killer.