A La-modified Lead Iron Titanate (Pb1-xLax)(Fe0.01Ti0.99)O-3 (x = 0, 4, 8, 12, 16 and 20%) (Lx-LITO) ceramics have been synthesized by sol-gel route. The structural properties of these compounds have been examined by XRD and Raman spectroscopy. The Optical properties of Lx-LITO have been investigated by UV- visible spectroscopy to evaluate their optical band gap (E-g). Moreover, we have studied in details the effect of dopant content (x%) on the structural and dielectric properties at a large range of temperature up to 600 degrees C and frequency 100 Hz-1MHz. At room temperature, Lx-LITO have relatively high real permittivity (epsilon') which increases from 250 to 850 with rising x% and insignificant dielectric losses (tan(delta) < 0.01 at 1 kHz). We have investigated the dielectric diffuse phase transition using Curie-Weiss law and modified Uchino law. The results indicate the appearance of relaxation behavior from x = 8% and the existence of dielectric anomalies from x = 16% at paraelectric phase. In addition, the ceramics Lx-LITO display a negative temperature coefficient NTC resistance as the case of a thermistor. Resistance-temperature characteristics (RTCs) are estimated by fitting thermistor equation. The results are in agreement with the suitable values, which indicate that for x < 16% these materials can be used in high-temperature thermistors and also for x > 16% at room-temperature thermistor applications. The effect of dopant content (x%) on NTC parameters is discussed and appears to be promising material for NTCR applications.