  We present eight new light curves of the transiting extra-solar planet
HAT-P-25b obtained from 2013 to 2016 with three telescopes at two
observatories. We use the new light curves, along with recent literature
material, to estimate the physical and orbital parameters of the transiting
planet. Specifically, we determine the mid-transit times (T$_{C}$) and update
the linear ephemeris, T$_{C[0]}$=2456418.80996$\pm$0.00025
[$\mathrm{BJD}_\mathrm{TDB}$] and P=3.65281572$\pm$0.00000095 days. We carry
out a search for transit timing variations (TTVs), and find no significant TTV
signal at the $\Delta T=$80 s-level, placing a limit on the possible strength
of planet-planet interactions ($\mathrm{TTV_{G}}$). In the course of our
analysis, we calculate the upper mass-limits of the potential nearby
perturbers. Near the 1:2, 2:1, and 3:1 resonances with HAT-P-25b, perturbers
with masses greater than 0.5, 0.3, and 0.5 $\mathrm{M_{\oplus}}$ respectively,
can be excluded. Furthermore, based on the analysis of TTVs caused by light
travel time effect (LTTE) we also eliminate the possibility that a long-period
perturber exists with $M_{\rm p}> 3000 \,\mathrm{M_{J}}$ within $a=11.2\,{\rm
AU}$ of the parent star.
