The deal includes refinancing Capsugel's existing debt of $2 billion and is set to be finalised by the second quarter of 2017, Lonza said in a statement.
Buying Capsugel "meets Lonza's strategic and financial goals", chief executive Richard Ridinger said in the statement.
"It accelerates our healthcare continuum strategy by giving us broader exposure to the fast-growing pharma and consumer healthcare markets," he added.
Both companies' boards of directors have approved the deal.
Lonza said that within three years it expected to achieve 30 million francs (27.9 million euros, $29.3 million) per year in operating synergies and 15 million francs in tax synergies a year.
Capsugel, which is based in New Jersey, was purchased from Pfizer in 2011 by private equity firm KKR.