The U.S. dollar has climbed 23 percent against a trade-weighted basket of global currencies in the last year. In first-quarter earnings reports, American corporations across a variety of sectors have cited the challenges posed by currency strength.
Read MoreUgh: Fed offers tepid view of economy
"Some pretty unique things," including a labor dispute that gridlocked some West Coast ports and rough winter weather, tripped up the wider U.S. economy in the first quarter, Lew said. He remains optimistic despite the IMF on Tuesday cutting its full-year U.S. growth outlook to 3.1 percent, from 3.6 percent previously.
"I feel pretty confident that the U.S. economy will do pretty well for the rest of the year," Lew said.
A string of sluggish consumer indicators has also fueled doubts about sustained growth in the U.S. Declining retail sales throughout the winter months—despite cheap oil putting more money in consumer pockets—have raised concerns.
But disappointing consumer readings may not prove dire, Lew said. If Americans pay down debt with extra money rather than spend it, it may provide a long-term boon, he said.
Some market watchers have recently warned that a troubling lack of liquidity lingers underneath the relative strength of the U.S. economy. Former Treasury secretaries Larry Summers and Henry Paulson, among others, have outlined the risks present in currency and Treasury market volatility.
Read MorePaulson joins chorus of concern about liquidity
Lew noted that the Treasury has monitored market liquidity, including the possible causes of a sharp plunge in bond yields in October.
"We are constantly watching the factors that are at work that affect market liquidity," Lew said.
He noted that geopolitical concerns at the time and a "huge amount" of electronic trading may have contributed to the movement. Lew added that he doesn't believe the regulatory environment was "the predominant factor" driving the volatility.