Citicorp and Chase Manhattan Corp., holding companies for the nation's second and third largest banks, today reported first-quarter earnings that basically were flat compared with the same period a year ago.

By contrast, BankAmerica Corp., parent of the world's largest bank, reported on Monday that the first-quarter earnings were up 17 per cent over the year before.

Citicorp said it operating earnings before securities gains and losses totaled $92.1 million (74 cents a share) in the first quarter, up only 1.4 per cent from the same period last year when it earned $90.8 million (73 cents). After taking into account securities transactions, net income was $88.5 million (71 cents) compared with $89.7 million (72 cents) in the first three months of 1976.

The small increase in operating earnings in the first quarter was attributed primarily to an improvement in net interest revenue, and a $5 million decrease in the size of the loan loss provision over the same quarter last year. These gains were offset by a $17 million negative swing in profits from Citibank's trading account in government securities.

Chase Manhattan, meanwhile, reported that its first-quarter income before securities transactions was $27.4 million, an increase of less than 1 per cent over the $27.2 million earned in the same three-month period in 1976. Earnings per share amounted to 85 cents in both quarters. Net income after securities transactions for the quarter rose to $28.9 million (90 cents a share) compared with $24.7 million (77 cents) in the comparable period last year.

A lower provision for loan losses in the first quarter largely was offset by reduced net interest income as a result of weak domestic loan demand and a lower level of interest rates during the period, which accounted for the flat results at Chase.

The provision for loan losses was $65 million compared with $82.7 million in the first quarter of 1976. Actual loan losses totaled $61 million, the bulk of it in real estate.

BankAmerica earnings before securities transactions totaled $82.8 million (57 cents a share) in the first quarter, up from $70.5 million (51 cents) in the same period a year ago. After securities trading, net income rose to $83 million (87 cents) from $70.8 million (51 cents) in 1976 first quarter.

The bank holding company attributed the earnings jump to a significant drop in its loan loss provision, a decline in its effective tax rate, and a number of other factors. Net loan chargeoffs were $23.5 million, down from $31.1 million in the first three months of last year.