Analysts polled by Swiss financial newswire AWP had expected the group's net income for the first six months of 2013 to be between $1.8-2.0 billion.
From April to June, net profit was down 27 percent to $789 million compared to last year's second quarter, the insurer said in a statement.
The group's first-half operating profit was down by nine percent to $2.2 billion compared with the same period last year.
Its combined ratio — a measure of an insurers' profitability — increased slightly to 95.6 percent from 94.8 percent in the first half of 2012.
The insurer said it had achieved these results in a period "characterized by natural catastrophes and large weather-related events", such as widespread flooding in central Europe and tornadoes in the United States, including a deadly twister in Oklahoma in May.
Zurich Insurance was still feeling the challenges of a weak global economy, the group added.
"The economic environment remains challenging with continued low interest rates exerting pressure on our investment income," chief executive officer Martin Senn said in the statement.
The group said it was on track to meet some of its targets, such as those set for Global Life and expense savings.
But it said targets for General Insurance and Farmers "remain more challenging".
Zurich announced on that it had named company insider Kristof Terryn as chief executive of its global life division with immediate effect.
Terryn, a Belgian who joined Zurich in 2004, replaces American Kevin Hogan, who the group said had decided to pursue new opportunities.
Hogan had been with Zurich since 2008, and was named chief executive of its life insurance wing in 2010.
Terryn currently heads Zurich's operations and is a member of its executive committee.
Markus Nordlin, a Finnish and US citizen who is currently the group's chief information technology officer, is to temporarily take charge of its operations in the wake of Terryn's appointment.