Tomato culture is very nitrogen demanding and periodical evaluation of the nutritional state of tomato plants can help in handling nitrogen fertilization. Determining the relative content of chlorophyll using a chlorophyll meter or soil plant analysis development (SPAD) has come up as an alternative method among the common methods. The aim of this study was to determine the relative chlorophyll index in the leaf blade of tomato plants 'BRS Zamir' in response to nitrogen doses throughout 112 days in a protected environment. A randomized delimitation was used with subdivided parcels in time with four replications. The parcels (two plants) received treatment constituted by 5 Nitrogen (N) doses: 80, 160, 240, 320 and 400 kg ha -1 of N, using urea as source. The doses were divided and applied on the 14th, 28th, 42nd, 56th, 70th, 84th, 98th and 112nd days after transplant. Determination of relative content of chlorophyll was done using a portable meter, with readings in the following schedule: 7:00 a.m, 9:00 a.m, 11:00 a.m, 1:00 p.m, 3:00 p.m and 5:00 p.m. The data were subjected to analysis of variance by Ftest at 5% probability, and when they were significant, they were analyzed by a regression. The study verified that relative content of chlorophyll presented a positive correlation of 0.84 with content of total N, and the dose increments of N influenced the chlorophyll content in leaf blade.