The group saw pre-tax profits drop to £20.1 million in the six months to February 28 from £25.7 million a year earlier despite notching up a 34% hike in retail sales to £481.7 million.
Chief executive Nick Robertson said the group has "never been about the short-term" as he put faith in a ramped-up £68 million investment plan this financial year to double annual sales capacity to £2.5 billion.
ASOS, which stands for As Seen On Screen, warned last month that costs of new warehousing in the UK and Germany as well as start-up expenses in China would hit profits.
More than a fifth of its stock market value was wiped off at one stage after the warning in March and as its second quarter sales growth failed to match forecasts.
But Mr Robertson said: "This increased pace of investment has reduced our profitability in the period, but will deliver significantly increased capacity as well as efficiencies in the longer term.
"The scale of the global opportunity remains as exciting as ever and we are investing for the many opportunities ahead."