The gain was also 38,000 more than economists had predicted and marks the fourth consecutive month private sector job gains have increased. It also topped November's 229,000 new jobs, which had been the second highest tally for the year.
The payroll firm's monthly report is issued two days before the Labor Department's monthly Employment Situation report, which includes public sector jobs and determines the succinct unemployment rate, a sharply-focused measure of how the labor market is performing.
In the private sector reports published by ADP, jobs increased by an average of 197,000 jobs per month.
In December, companies with under 50 employees added 108,000 jobs, while firms with 50 to 499 employees added 59,000. The largest firms, with a workforce of 500 or more, added 71,000 jobs in the month.
In another breakdown, ADP said goods-producing companies added 69,000 jobs in December, while service-oriented firms added 170,000.
Construction jobs rose by 48,000 in December, while manufacturing added 19,000 jobs. Under trade, transportation and utilities, companies added 47,000 jobs in the month.
Financial firms added 10,000 jobs in the month, while professional business services jobs rose by 53,000.