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The nearby (6.5 pc) star HD 219134 was recently shown by Motalebi et al.(2015) and Vogt et al. (2015) to host several planets, the innermost of whichis transiting. We present twenty-seven years of radial velocity observations ofthis star from the McDonald Observatory Planet Search program, and nineteenyears of stellar activity data. We detect a long-period activity cycle measuredin the Ca II $S_{HK}$ index, with a period of $4230 \pm 100$ days (11.7 years),very similar to the 11-year Solar activity cycle. Although the period of theSaturn-mass planet HD 219134 h is close to half that of the activity cycle, weargue that it is not an artifact due to stellar activity. We also find asignificant periodicity in the $S_{HK}$ data due to stellar rotation with aperiod of 22.8 days. This is identical to the period of planet f identified byVogt et al. (2015), suggesting that this radial velocity signal might be causedby rotational modulation of stellar activity rather than a planet. Analysis ofour radial velocities allows us to detect the long-period planet HD 219134 hand the transiting super-Earth HD 219134 b. Finally, we use our long timebaseline to constrain the presence of longer-period planets in the system,excluding to $1\sigma$ objects with $M\sin i>0.36 M_J$ at 12 years(corresponding to the orbital period of Jupiter) and $M\sin i>0.72 M_J$ at aperiod of 16.4 years (assuming a circular orbit for an outer companion).

A 12-Year Activity Cycle for HD 219134